Stack001.cpp

#include <string>

using namespace std;

struct Stack
{
    char x;
    Stack* prev;
};

typedef Stack* ps;

void push(ps &top, char c)
{
    ps s = new Stack;
    
    s->x = c;
    s->prev = top;
    
    top = s;
}

char pop(ps &top)
{
    ps s = top;
    char c = top->x;

    top = s->prev;
    delete s;

    return c;
}

bool isEmpty(ps top)
{
    return top == nullptr;
}

void destructList(ps top)
{
    while (!isEmpty(top)) {
        pop(top);
    }
}

bool checker(char* s)
{
    ps top = nullptr;
    int i, l = strlen(s);
    bool es = false;

    for (i = 0; i < l; i++) {
        if (s[i] == '(') {
            push(top, s[i]);
        }
        else if (s[i] == ')') {
            if (isEmpty(top)) {
                
                destructList(top);
                return false;
            }
            pop(top);
        }
    }

    es = isEmpty(top);
    destructList(top);
    
    return es;
}