Verify balanced brackets, parenthesis and others.

balanced.c

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

#define IGNORE 0
#define OPEN 1
#define CLOSE 2

int isOpenChar(char c){
  switch(c){
     case '(':
     case '{':
     case '[':
     case '<':
     return OPEN;
     case ')':
     case '}':
     case ']':
     case '>':
     return CLOSE;
  }
  return IGNORE;
}

int getWeight(char c){
  switch(c){
     case '(':
     case ')':
       return 1;
     case '{':
     case '}':
       return 2;
     case '[':
     case ']':
       return 3;
     case '<':
     case '>':
       return 4;
  }
  return 0;
}

typedef struct Node_{
  int w;
  struct Node_* next;
  struct Node_* anterior;
} Node;

typedef struct Queue{
  Node* first;
  Node* last;
}Queue;

void push(Queue* q, int w){
  Node* newNode = (struct Node_*) malloc(sizeof(struct Node_));
  newNode->w = w;
  if(q->first == NULL){
    q->first = q->last = newNode;
  }
  else{
    newNode->anterior = q->last;
    q->last->next = newNode;
    q->last = newNode;
  }
}

int pop(Queue* q){
  if(q->first == NULL || q->last == NULL){
    return -1;
  }

  Node* oldLast = q->last;
  int w = oldLast->w;
  q->last = oldLast->anterior;
  if(q->last != NULL)
    q->last->next = NULL;
  if(q->last == NULL)
    q->first = NULL;
  free(oldLast);
  return w;
}
void print(Queue* q){
  if(q == NULL || q->first == NULL)
    return;
  Node* n = q->first;
  int c = 0;
  while(n != NULL){
    printf("%i,", n->w);
    n = n->next;
  }
  printf("\n");
}
void clear(Queue* q){
  if(q == NULL || q->first == NULL)
    return;
  Node* n = q->first;
  Node* aux = n;
  while(n != NULL){
    aux = n->next;
    free(n);
    n = aux;
  }
}

bool isEmpty(Queue* q){
  return q->first == NULL;
}

bool isBalanced(char* text){
  int length = strlen(text);
  Queue* q = (Queue*) malloc(sizeof(Queue));
  q->first = NULL;
  q->last = NULL;
  bool balanced = true;
  for(int i = 0; i < length; i++){
    char c = text[i];
    int type = isOpenChar(c);
    int w = getWeight(c);
    if(type == OPEN)
      push(q, w);
    else if(type == CLOSE && pop(q) != w){
      balanced = false;
      break;
    }
  }
  balanced = balanced ? isEmpty(q) : false;
  clear(q);
  free(q);
  return balanced;
}

void test(char* t){
  bool balanced = isBalanced(t);
  if(balanced)
    printf("%s is balanced", t);
   else
    printf("%s is NOT balanced", t);
  printf("\n");
}

int main(void) {
  test("");
  test("hjkh");
  test("[");
  test("<");
  test("()");
  test("<>");
  test(")(");
  test("><");
  test("[{}]");
  test("<()>");
  test("<(>");
  test("{<}>");
  
  test("t(t{t}t)t");
  
  
  return 0;
}