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@mycodeschool
Created October 29, 2013 00:49
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C++ Program to check for balanced parentheses in an expression using stack.
/*
C++ Program to check for balanced parentheses in an expression using stack.
Given an expression as string comprising of opening and closing characters
of parentheses - (), curly braces - {} and square brackets - [], we need to
check whether symbols are balanced or not.
*/
#include<iostream>
#include<stack>
#include<string>
using namespace std;
// Function to check whether two characters are opening
// and closing of same type.
bool ArePair(char opening,char closing)
{
if(opening == '(' && closing == ')') return true;
else if(opening == '{' && closing == '}') return true;
else if(opening == '[' && closing == ']') return true;
return false;
}
bool AreParanthesesBalanced(string exp)
{
stack<char> S;
for(int i =0;i<exp.length();i++)
{
if(exp[i] == '(' || exp[i] == '{' || exp[i] == '[')
S.push(exp[i]);
else if(exp[i] == ')' || exp[i] == '}' || exp[i] == ']')
{
if(S.empty() || !ArePair(S.top(),exp[i]))
return false;
else
S.pop();
}
}
return S.empty() ? true:false;
}
int main()
{
/*Code to test the function AreParanthesesBalanced*/
string expression;
cout<<"Enter an expression: "; // input expression from STDIN/Console
cin>>expression;
if(AreParanthesesBalanced(expression))
cout<<"Balanced\n";
else
cout<<"Not Balanced\n";
}
@pankaj031197
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hii

@Mandana24
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Python 3.0 - Check if the Parenthesis are balance

def CheckBalancedParenthesis(exp):
n = len(exp)
#Create a stack: - S
S = []

for i in range(n):
    if exp[i] in {'(','{','['}:
        S.append(exp[i])
    elif exp[i] in {')','}',']'}:
        if (len(S)== 0) or (S[-1] + exp[i] not in {'()','{}','[]'}):
            return False
        else: 
            S.pop()
return len(S)== 0

@stevefan1999-personal
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long c++11 version

#include <string>
#include <vector>
#include <iostream>

#define $$(expr) { return (expr); }

bool is_balanced(const std::string str) {
    std::vector<char> stack;
    
    auto is_paren_open = [](const char c) $$(c == '(' || c == '[' || c == '{');
    auto is_paren_close = [](const char c) $$(c == ')' || c == ']' || c == '}');
    auto paren_convert = [](const char c) $$(
        c == '(' ? ')' : 
        c == '[' ? ']' : 
        c == '{' ? '}' : 
        c == ')' ? '(' :
        c == ']' ? '[' :
        c == '}' ? '{' : 
        0
    );

    for (auto c : str) {
        const bool open = is_paren_open(c);
        const bool close = is_paren_close(c);

        if (!open && !close) {
            return false;
        }

        if (open) {
            stack.push_back(c);
        }

        if (close) {
            if (stack.size() > 0) {
                auto top = stack.back();
                if (top != paren_convert(c)) {
                    return false;
                }
                stack.pop_back();
            } else {
                return false;
            }
        }
    }

    return stack.size() == 0;
}

@NorahB21
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NorahB21 commented Nov 8, 2017

Hello, I can't find any solution for my wired errors ,I tried doing it on java in jgrasp ide but I have errors .
my errors:
BalancedParan.java:74: error: illegal character: '\u00a0'
    if(open == '(' && close == ')')
^
BalancedParan.java:74: error: illegal character: '\u00a0'
    if(open == '(' && close == ')')
^
BalancedParan.java:74: error: illegal character: '\u00a0'
    if(open == '(' && close == ')')
^
BalancedParan.java:74: error: illegal character: '\u00a0'
    if(open == '(' && close == ')')
^
BalancedParan.java:74: error: ';' expected
    if(open == '(' && close == ')')
^
BalancedParan.java:74: error: not a statement
    if(open == '(' && close == ')')
^
BalancedParan.java:74: error: ';' expected
    if(open == '(' && close == ')')
^
7 errors

my full code:
import java.util.*;
import java.util.Stack;

public class BalancedParan
{

public static void main(String[] args)
{

System.out.println(isBalanced("[(12)(34)]+[(5+6)(7*8)]"));
System.out.println("exp1: {()}");
System.out.println(isBalanced("{()}"));

  System.out.println("exp2: {{)) ");

System.out.println(isBalanced("{{))"));

}
private static boolean isBalanced(String expression)
{

char[] c = expression.toCharArray();
Stack s= new Stack ();

for(int i=0; i< c.length; i++)
{

 if(c[i] == '{' || c[i] == '(' || c[i] == '[')
s.push(c[i]);

else if(c[i] == '}' || c[i] == ')' || c[i] == ']')
{

  if(isMaching(s.peek(),c[i])== true)
   {
   
     s.pop();         
     System.out.println("not balanced");
   }
   else
   return false;
    System.out.println("balanced");



}//end if

} //end for

if(s.isEmptyStack())
{
return true;}

 else{
 
 return false;}

}//end isBalanced

public boolean isEmptyStack()
{
return (stack == null);
}//end isEmptyStack

public boolean isFullStack()
{
return false;
}//end isFullStack

public boolean isMaching(char open, char close)
{
    if(open == '(' && close == ')')
{
return true;
}
if(open == '[' && close == ']')
{
return true;
}
if(open == '{' && close == '}')
{
return true;
}

else{
return false;
}

}

}//end class

I will highly appreciate the help..

@Aman2306
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// TRY THIS

#include<stdio.h>
#include<string.h>

#define MAX 50
char top = -1, stack[MAX];

int full(){
if(top == MAX-1)
return 1;
return 0;
}

int empty(){
if(top == -1)
return 1;
return 0;
}

void push(char item){
if(full())
{
printf("Stack is full\n");
return;
}
else{
stack[++top] = item;
}
}

char pop(){
if(empty()){
printf("Stack is empty\n");
return -1;
}
return stack[top--];
}

void display(){
if(empty()){
printf("Stack is empty\n");
return;
}
else{
while(!empty()){
printf("%c ", pop());
}
}
}

void peek(){
if(empty()){
printf("Stack is empty\n");
return;
}
else
printf("%c", stack[top]);
}

char pair(char c){
if(c == ')')
return '(';
else if(c == '}')
return '{';
else
return '[';
}
int main(){
int i;
char ch, x;
char exp[50];
gets(exp);
for(i=0; i<strlen(exp); i++)
{
if(exp[i] == '(' || exp[i] == '[' || exp[i] == '{'){
push(exp[i]);
}
else if(exp[i] == ')' || exp[i] == '}' || exp[i] == ']'){
if(empty()){
printf("NO OPENING BRACKET...INVALID EXPRESSION\n");
return -1;
}
else{
x = pair(exp[i]);
if(pop() != x){
printf("NO MATCHING..INVALID EXPRESSION\n");
return -1;
}
}
}
}
if(!empty()){
printf("LEFT PARENTHESIS ARE MORE THAN RIGHT....INVALID EXPRESSION\n");
}
return 0;
}

@vishwasjha17
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bool is_balanced(string expression) {
stack s;
for (char c : expression) {
if (c == '{') s.push('}');
else if (c == '[') s.push(']');
else if (c == '(') s.push(')');
else {
if (s.empty() || c != s.top())
return false;
s.pop();
}
}
return s.empty();
}

@nihal-singh
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Here's my solution @mycodeschool

string isBalanced(string s) {
     stack<char> temp;
    for (int i=0;i<s.length();i++){
        if(s[i] == '(' || s[i] == '[' || s[i] == '{')temp.push(s[i]);
        else if(!temp.empty()){
            if((temp.top() == '{' && s[i] == '}') || (temp.top() == '[' && s[i] == ']') || (temp.top() == '(' && s[i] == ')'))temp.pop();
            else return "NO";
        }
        else return "NO";
    }
    return temp.empty() ? "YES" : "NO";
}

@ahmedmohyh
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#include
#include
using namespace std;
void balanced (char *A, int n){
stack s;
for (int i = 0 ; i<n; i++) {
if( A[i] == '(' || A[i] =='{' || A[i] =='[')
s.push(A[i]);
else if (A[i] == ')' || A[i] =='}' || A[i] ==']'){
if (s.empty()) {cout<<"not balanced"<<endl; return;}
else if (s.top()=='(' && A[i] == ')') s.pop();
else if(s.top()=='[' && A[i] == ']') s.pop();
else if (s.top()=='{' && A[i] == '}') s.pop();
else{cout<<"not balanced"<<endl; return; }}
}
if (s.empty()) cout<<"balanced"<<endl;
else cout<<"not balaned"<<endl;

	}

int main() {
char arr[20];
cout<<"please enter the expression you want to check"<<endl;
cin.getline (arr,20);
int r = strlen(arr);
balanced(arr,r);
return 0; }

@Yashaggarwal35
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//TRY THIS OUT

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int top = -1;
char s[100];

void balanced_parentheses(){
int i,l;
char exp[100],x,y;
printf("Enter the exp: \n");
scanf("%s",exp);
l = strlen(exp);
for(i = 0;i<l;i++){
if(exp[i]=='(' || exp[i]=='{' || exp[i]=='['){
x = exp[i];
push(exp[i]);
}
else if(exp[i]==')' || exp[i]=='}' || exp[i]==']'){
y = exp[i];
pop(y);
}
}
}

void push(char x){
top++;
s[top] = x;
}

void pop(char y){
if(y==')'){
if(s[top]=='('){
top=top-1;
}
}
else if(y=='}'){
if(s[top]=='{'){
top = top-1;
}
}
else if(y==']'){
if(s[top]=='['){
top = top-1;
}
}
else{
return "\0";
}
}

void Print(){
int i;
if(top==-1){
printf("\nThey are balanced parentheses");
}
else{
printf("\nFALSE! not balanced ones..because\n");

    for(i=0;i<=top;i++){
        if(s[top]=='('){
                printf("You should end with: ')' ");
           }
        else if(s[top]=='{'){
            printf("You should end with: '}' ");
        }
        else if(s[top]=='['){
            printf("You should end with: ']'");
        }
        else{
            printf("INVALID expression here!");
        }
        return;
    }

}

}

int main(){
balanced_parentheses();
Print();
}

@suresh68
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// try this out

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stdbool.h>
struct node
{
char data;
struct node* next;
};
struct node* top = NULL;
void push(char x)
{
struct node* temp = (struct node*)malloc(sizeof(struct node));
temp->data = x;
temp->next = top;
top = temp;
}
void pop()
{
struct node* temp = top;
if(top == NULL)
{
return;
}
temp = top;
top = top->next;
free(temp);
}
bool arepair(char opening,char closing)
{
if(opening == '(' && closing == ')') return true;
else if(opening == '{' && closing == '}') return true;
else if(opening == '[' && closing == ']') return true;
else return false;
}
bool checkbalancepar(char arr,int length)
{
int i;
for(i=0;i<length;i++)
{
if(
(arr+i)=='{'||(arr+i)=='['||(arr+i)=='(')
{
push((arr+i));
}
else if(
(arr+i)=='}'||(arr+i)==']'||(arr+i)==')')
{
if(top==NULL||!arepair(top->data,(arr+i)))
{
printf("paranthesis doesn't match\n");
return false;
}
else
{
pop();
}
}
}
return (top==NULL)? true:false;
}
void print(struct node
top)
{
struct node* temp = top;
if(top == NULL)
{
printf("the stack is empty\n");
return;
}
while(temp!= NULL)
{
printf("%c ",temp->data);
temp = temp->next;
}
printf("\n");
}
int main()
{
char *arr;
int num,i;
printf("ener the no paranthesis elements: ");
scanf("%d",&num);
arr = (char ) calloc(num,sizeof(char));
printf("enter the string: ");
for(i=0;i<num;i++)
{
scanf("%c ",(arr+i));
}
for(i=0;i<num;i++)
{
printf("%c ",
(arr+i));
}
if(checkbalancepar(arr,num))
{
printf("balanced parenthesis\n");
}
else
printf("unbalanced paranthesis\n");
print(top);
return 0;
}

@suresh68
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@

Hello guys.. I have implemented the same in C using stack. The following is my code. It's having no issues as far as pushing data is concerned, however, it doesn't seem to pop the data.. Please help me out debug this code

// Stacks: Check for balanced paranthesis

include<stdio.h>

include<stdlib.h>

define MAX_SIZE 100

char c[MAX_SIZE] ;
struct Node {
char data;
struct Node * next;
};
struct Node * top = NULL ;
void Push(int data){
struct Node * temp = (struct Node *)malloc(sizeof(struct Node));
temp->data = data;
temp->next = top ;
top = temp ;
}

void Pop(){
if(top == NULL){
printf("There are no items in the stack to pop\n");
return;
}
struct Node * temp = top;
top = top->next ;
free(temp);
}

void Print(){
if(top == NULL){
printf("Stack is empty\n");
}
struct Node * temp = top ;
printf("\nThe current stack is: ");
while(temp != NULL){
printf(" %c",temp->data);
temp = temp->next ;
}
printf("\n");
}

void CheckforBalancedparanthesis(char c[], int length){
//now as we scan the expression push the character into the stack
int i;
for(i=0;i<length;i++){
if((c[i] == '(' ) || (c[i] == '{' ) || (c[i] == '[' ))
{
Push(c[i]);
}
else if((c[i] == ')' ) || (c[i] == '}' ) || (c[i] == ']' ))
{
if((top == NULL) || (c[i] != top->data))
{
printf("Paranthesis don't match \n");
return ;
}
else{
Pop();
}
}
printf(" %c",top->data);
}
return (top == NULL)?("Paranthesis match"):("Parenthesis don't match") ;
}
int main(){
int length;
printf("Enter a string of paranthesis: ");
scanf("%s",c);
//printf("%s",c);
length = strlen(c);
CheckforBalancedparanthesis(c,length);
Print(top);
//Pop();Print(top);Pop();Print(top);
//Push(3);Push(4);Push(1);Push(7);Print(top);Pop();Print(top);Pop();Print(top);
}

sir u haven't compared the previous paranthesis with the current paranthesis entered that why it is throwing the error while popping
//Try this out
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<stdbool.h>
struct node
{
char data;
struct node* next;
};
struct node* top = NULL;
void push(char x)
{
struct node* temp = (struct node*)malloc(sizeof(struct node));
temp->data = x;
temp->next = top;
top = temp;
}
void pop()
{
struct node* temp = top;
if(top == NULL)
{
return;
}
temp = top;
top = top->next;
free(temp);
}
bool arepair(char opening,char closing)
{
if(opening == '(' && closing == ')') return true;
else if(opening == '{' && closing == '}') return true;
else if(opening == '[' && closing == ']') return true;
else return false;
}
bool checkbalancepar(char arr,int length)
{
int i;
for(i=0;i<length;i++)
{
if(
(arr+i)=='{'||(arr+i)=='['||(arr+i)=='(')
{
push((arr+i));
}
else if(
(arr+i)=='}'||(arr+i)==']'||(arr+i)==')')
{
if(top==NULL||!arepair(top->data,(arr+i)))
{
printf("paranthesis doesn't match\n");
return false;
}
else
{
pop();
}
}
}
return (top==NULL)? true:false;
}
void print(struct node
top)
{
struct node* temp = top;
if(top == NULL)
{
printf("the stack is empty\n");
return;
}
while(temp!= NULL)
{
printf("%c ",temp->data);
temp = temp->next;
}
printf("\n");
}
int main()
{
char *arr;
int num,i;
printf("ener the no paranthesis elements: ");
scanf("%d",&num);
arr = (char ) calloc(num,sizeof(char));
printf("enter the string: ");
for(i=0;i<num;i++)
{
scanf("%c ",(arr+i));
}
for(i=0;i<num;i++)
{
printf("%c ",
(arr+i));
}
if(checkbalancepar(arr,num))
{
printf("balanced parenthesis\n");
}
else
printf("unbalanced paranthesis\n");
print(top);
return 0;
}

@ALisaeed909
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX 100

char stack_A[MAX];
int c;
int top =-1;

char push(char c){
if(top==MAX-1){
printf("Erorr is overflow\n");
}
top ++;
stack_A[top] = c;
return c;
}
char pop(){
if(top==-1){
printf("Error of lowerflow\n");
}
top--;
}

int main(){
char exp[MAX];
printf("Enter the thing\n");
scanf("%s",exp);
int i;
for(i=0;i<strlen(exp);i++){
if(exp[i]=='('||exp[i]=='{'||exp[i]=='['){
push(exp[i]);
}
else if (exp[i]==')'||exp[i]=='}'||exp[i]=="]"){
if (top == -1 || exp[i] != c){

        }
    }    else{
             pop();
     }
}

if (top == -1){
    printf("True\n");
} else{
    printf("False\n");
}

}

@komal14prasad
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Can you share the code in Java, I tried implementing the same logic in java but unable to develope one

@jazimabbas
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Please anyone give me examples of data structures. Because practise makes a man perfect so plz help me out. Thanks in advance

@Rohith-Rajan
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This is my version of the code

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <string>
#include <stack>

using namespace std;

char openingBracket(char closing_bracket)
{
    char opening_bracket;
    if (closing_bracket == '}') 
      return '{' ;
    else if (closing_bracket == ')') 
     return '(' ;
    else if (closing_bracket == ']') 
     return '[' ;
}
void areParenthesisBalanced(string name)
{
    stack<char> S;
    bool isBalanced = true;
    for(int i=0;i<name.length();i++)
    {
        if( name[i] == '(' || name[i] == '{' || name[i] == '[' )
        {
        S.push(name[i]);
        }
        else if(name[i] == '}' || name[i] == ')' || name[i] == ']')
        {
            if( (S.empty() && i!=name.length()) || (S.top()!= openingBracket(name[i]) ))
            {
               isBalanced = false;
               break;
            }
            else
            {
               S.pop();
            }
        }
    }
    if(isBalanced)
    {
        cout<<"\n The expression is balanced!!\n";
    }
    else if(!isBalanced)
    {
       cout << "The expression is not balanced!\n";
    }
    
}
int main()
{
    string name ;
    cout<<"Enter an expression:";
    getline(cin,name);
    areParenthesisBalanced(name);

    return 0;
}

@nimalatifi
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hi guys.
i think you missed one important issue.

Did you ever attempt to inserting closing bracket before opening?!!

@senthilnathan87
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senthilnathan87 commented Aug 26, 2019

Can you share the code in Java, I tried implementing the same logic in java but unable to develope one

import org.testng.Assert;
import org.testng.annotations.Test;
import java.util.Stack;
/**
 * ExpressionEvaluator
 */
public class ExpressionEvaluator {

    @Test
    public void expressionsTest() {
        Assert.assertTrue(BalancedExpressionAlg.isBalanced("{A+B}"));
        Assert.assertTrue(BalancedExpressionAlg.isBalanced("{ (C*9) * [10] - (A+B) }"));
        Assert.assertFalse(BalancedExpressionAlg.isBalanced("{ { () }"));
        Assert.assertTrue(BalancedExpressionAlg.isBalanced("{ as } (C*2)"));
        Assert.assertFalse(BalancedExpressionAlg.isBalanced("}{"));
    }
    
}

class BalancedExpressionAlg {

    // Works in O(n)
    static boolean isBalanced(String expr) {
        Stack<Character> stack = new Stack<>();
        char[] chars = expr.toCharArray();
        for(char ch : chars) {
            if(ch == '{' || ch == '[' || ch == '(') {
                stack.push(ch);
            }
            switch(ch) {
                case '}':
                    if(stack.isEmpty() || stack.pop() != '{') return false;
                break;
                case ']':
                    if(stack.isEmpty() || stack.pop() != '[') return false;
                break;
                case ')':
                    if(stack.isEmpty() || stack.pop() != '(') return false;
                break;                                 
            }

        }
        if(stack.isEmpty()) {
            return true;
        }
        return false;
    }
}

@misterpoloy
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This was my solution:

#include <iostream>
#include <stack>
#include <string>

bool testBalance(std::string str) {
    std::stack<char> expressions;
    for (int i = 0; i < str.size(); i++) {
        char current = str[i];
        if (current == '{' || current == '[' || current == '(') {
            expressions.push(current);
            continue;
        }
        if (current == '}' || current == ']' || current == ')') {
            if (expressions.empty()) {
                return false;
            } else {
             // Compare the match
                char last = expressions.top();
                bool congruent = false;
                switch (last) {
                    case '{':
                        if (current == '}')
                            congruent = true;
                        break;
                    case '[':
                        if (current == ']')
                            congruent = true;
                        break;
                    case '(':
                        if (current == ')')
                            congruent = true;
                        break;
                    default:
                        break;
                }
                if (congruent) {
                    expressions.pop();
                } else {
                    return false;
                }
            }
        }
    }
    return expressions.empty();
};

int main() {
    std::string str;
    getline(std::cin, str);
    std::cout << testBalance(str) << std::endl;
    return 0;
}

@asad2200
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asad2200 commented Apr 21, 2020

Here the java code ,if someone wants

//------------------------------------

import java.util.Scanner;
import java.util.Stack;

public class CheckParathese {

static boolean checkPair(char opening,char closing){
    if(opening == '(' && closing == ')') return true;
    else if(opening == '{' && closing == '}') return true;
    else if(opening == '[' && closing == ']') return true;
    return false;
}

static boolean isBalanced(String s) {
    char arr[] = s.toCharArray();
    Stack<Character> st = new Stack<Character>();
    for(int i=0;i<s.length();i++){
        if(arr[i] == '(' || arr[i] == '{' || arr[i] == '[')
            st.push(arr[i]);
        else if(arr[i] == ')' || arr[i] == '}' || arr[i] == ']'){
            if(st.empty() || !checkPair(st.peek(),arr[i])){
                return false;
            }else
                st.pop();
        }
    }
    return st.empty()?true:false ;
}

public static void main(String[] args) throws Exception {
    String s;
    Scanner sc = new Scanner(System.in);
    s=sc.nextLine();
    sc.close();
    if(isBalanced(s))
        System.out.print("Paranthases are balanced");
    else
        System.out.print("Paranthases are not balanced");   
}

}
//-------------------------------------

@hitsa70
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hitsa70 commented Apr 29, 2020

import java.util.*;
public class Solution {

public static boolean matchingPeer(char open , char close){
if ( open == '(' && close == ')'){
return true;
}
if ( open == '[' && close == ']'){
return true;
}
if ( open == '{' && close == '}'){
return true;
}
// you can add more open and close rule

else{
return false;
}

}

public static boolean checkBalanced(String equation) 
{
	// Write your code here
	char[] c = equation.toCharArray();
Stack <Character> myStack= new Stack <Character> ();

for (int i = 0; i < c.length; i++)
{
	if(c[i]=='(' || c[i] == '[' || c[i] == '{'){
		myStack.push(c[i]);
        continue;
	}
	else if (c[i]== ')' || c[i]==']' || c[i] == '}'){
        	if(myStack.isEmpty())
                return false;
			if(matchingPeer(myStack.peek(),c[i]) == true){
				myStack.pop();
			
			} else {
				return false;
			}
	}
}
	if(myStack.isEmpty()){
		return true;
	}	
	else {
		return false;
	}
}

}

@FredLeg
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FredLeg commented May 19, 2020

JAVASCRIPT

function isParanthesesBalanced( expression ){
  let symbols = {
      'opening': ['(','[','{','«'],
      'closing': [')',']','}','»'],
      'isOpening': function( car ){
        return this.opening.indexOf(car)>=0
      },
      'isClosing': function( car ){
        return this.closing.indexOf(car)>=0
      },
      'isPair': function( opening, closing ){
        let i = this.opening.indexOf(opening)
        if( !(i>=0) ) return false
        return i == this.closing.indexOf(closing)
      }
  }
  let stack = {
    's':       [],
    'push':    function( car ){ this.s.push(car) },
    'pop':     function( car ){ this.s.pop(car) },
    'top':     function(){ return this.s[this.s.length-1] },
    'isEmpty': function(){ return this.s.length==0 }
  }
  for ( let car of expression ) {
    if( symbols.isOpening(car) )
      stack.push(car)
    else if( symbols.isClosing(car) ){
      if( stack.isEmpty() || !symbols.isPair( stack.top(), car ) )
        return false
      else
        stack.pop()
    }
  }
  return stack.isEmpty()
}

let expressions = [
  "[(a+b)*(c+d)]",
  "[()(])",
  "Elle dit « ouh là là » tout le temps.",
  "none",
  ""
]
for( exp of expressions ){
  console.log( exp +" • "+ isParanthesesBalanced(exp) )
}
[(a+b)*(c+d)] • true
[()(]) • false
Elle dit « ouh là là » tout le temps. • true
none • true
 • true

@siddharthmagadum16
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siddharthmagadum16 commented Jun 9, 2020

Here's my code. I implemented using stack . The stack is implemented using object oriented implementation using arrays.
`// Stack - ||Object oriented implementation|| using arrays
#include
using namespace std;
#define MAX_SIZE 4

class Stack
{
private:
int A[MAX_SIZE]; // array to store the stack
int top; // variable to mark the top index of stack.
public:
// constructor
Stack()
{
top = -1; // for empty array, set top = -1
}

// Push operation to insert an element on top of stack. 
void Push(int x) 
{
  if(top == MAX_SIZE -1) { // overflow case. 
		printf("Error: stack overflow\n");
		return;
	}
	A[++top] = x;
}

// Pop operation to remove an element from top of stack.
void Pop() 
{
	if(top == -1) { // If stack is empty, pop should throw error. 
		printf("Error: No element to pop\n");
		return;
	}
	top--;
}

// Top operation to return element at top of stack. 
int Top() 
{
	return A[top];
}

// This function will return 1 (true) if stack is empty, 0 (false) otherwise
int IsEmpty()
{
	if(top == -1) return 1;
	return 0;
}

// ONLY FOR TESTING - NOT A VALID OPERATION WITH STACK 
// This function is just to test the implementation of stack. 
// This will print all the elements in the stack at any stage. 
void Print() {
	int i;
	printf("Stack: ");
	for(i = 0;i<=top;i++)
		printf("%d ",A[i]);
	printf("\n");
}

};

int solve(){
Stack S;
char ch=getchar();
while(ch!='\n'){
if(ch=='{' || ch=='(' || ch=='['){
S.Push(ch);
}
else if(ch=='}' || ch==')' || ch==']'){
if(S.IsEmpty() || (S.Top()!='{' && ch=='}') || S.Top()!='(' && ch==')' || S.Top()!='[' && ch==']');
else S.Pop();
}
ch=getchar();
}
S.IsEmpty()?printf("Balanced\n"):printf("Not Balanced\n");
return 0;
}

int main()
{
printf("Enter string of braces:\n");
solve();
return 0;
}`

@diegoba90
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I'm having a hard time with this. How can i make it so that instead of having the user input the string of characters it instead reads it from a file that has lines of different expressions.

@rohitverma1999hack
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return S.empty() ? true:false; is kind of redundant (if true return true else return false).
It's not redundant
what if the input is "(".

@umamahesh33
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it will fail for the test case when we include the space in the user input because the taking of string input will not execute after a blank space

@shoaibrain
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shoaibrain commented Oct 9, 2020

`def balancedBrackets(string):
#remove all invalid characters. This is optional by the way.If your string only contains [{()}]. You don't have to change input string in any
way
string = [x for x in string if x in '[{()}]]']

stack = []

for char in string:
	if char in '([{':
		stack.append(char)
	else:
		if len(stack) == 0  or not arePair(stack[-1], char):
			return False
		else:
			stack.pop()
if len(stack) == 0:return True
return `False`

def arePair(opening,closing):
if opening == '(' and closing == ')':return True
elif opening == '[' and closing == ']': return True
elif opening == '{' and closing == '}':return True
return False
`

@BaseMax
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BaseMax commented Apr 11, 2021

@ibrahimBanat
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Solution Using JavaScript: you can also check the whiteboard and test from here:

class MultiBracketValidation {
  constructor() {
    this.stack = new Stack();
    this.opening = ["{", "(", "[", "<"];
    this.closing = ["}", ")", "]", ">"];
  }
  checkForValidation(input) {
    for (const char of input) {
      if (this.isOpening(char)) {
        this.stack.push(char);
      } else if (this.isClosing(char)) {
        if (
          this.stack.isEmpty() ||
          !this.isPair(this.stack.peek().value, char)
        ) {
          return false;
        } else {
          this.stack.pop();
        }
      }
    }
    return this.stack.isEmpty();
  }
  isOpening(char) {
    return this.opening.indexOf(char) >= 0;
  }
  isClosing(char) {
    return this.closing.indexOf(char) >= 0;
  }
  isPair(opening, closing) {
    return this.closing.indexOf(closing) === this.opening.indexOf(opening);
  }
}

@HarshKakran
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Hey, I am a beginner in programming, and tried to implement the pseudo code shared in the video using C++, can you guys share the reviews about the coding style.

bool checkBalancedParenthesis(string exp){
    stack<char> s;
    int n = exp.length();
    for(int i=0; i<n; i++){
        if (exp[i] == '{' || exp[i] == '(' || exp[i] == '['){
            s.push(exp[i]);
        }
        else if(exp[i] == '}' || exp[i] == ')' || exp[i] == ']'){
            if (s.empty())
            return false;
            switch (s.top())
            {
            case '(':
                if (exp[i] == ')')
                    {s.pop();
                    break;}
                else{
                    return false;
                }
            case '{':
                if (exp[i] == '}')
                    {s.pop();
                    break;}
                else{
                    return false;
                }
            case '[':
                if (exp[i] == ']')
                    {s.pop();
                    break;}
                else{
                    return false;
                }
            }
        }    
    }
    return s.empty()?true:false;
}

@AshAman999
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Hey, I am a beginner in programming, and tried to implement the pseudo code shared in the video using C++, can you guys share the reviews about the coding style.

bool checkBalancedParenthesis(string exp){
    stack<char> s;
    int n = exp.length();
    for(int i=0; i<n; i++){
        if (exp[i] == '{' || exp[i] == '(' || exp[i] == '['){
            s.push(exp[i]);
        }
        else if(exp[i] == '}' || exp[i] == ')' || exp[i] == ']'){
            if (s.empty())
            return false;
            switch (s.top())
            {
            case '(':
                if (exp[i] == ')')
                    {s.pop();
                    break;}
                else{
                    return false;
                }
            case '{':
                if (exp[i] == '}')
                    {s.pop();
                    break;}
                else{
                    return false;
                }
            case '[':
                if (exp[i] == ']')
                    {s.pop();
                    break;}
                else{
                    return false;
                }
            }
        }    
    }
    return s.empty()?true:false;
}

If you are waiting for the mentors to reply then they ain't goint to reply and apart from that yeah coding style looks good

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