合法括号【栈】

#include <cstdio>
#include <cstring>
#include <stack>
#include <iostream>
#include <algorithm>
using namespace std;

stack<char>s;

int main()
{
    char str[100];
    while (scanf("%s", &str)!=EOF)
    {
        while (!s.empty())s.pop();
        int flag = 1;
        int len = strlen(str);
        for (int i = 0; i < len; i++)                //判断输入的字符串中是否有不符合标准的字符
        {
            if (str[i] == ‘(‘ || str[i] == ‘{‘ || str[i] == ‘[‘ || str[i] == ‘)‘ || str[i] == ‘}‘ || str[i] == ‘]‘)
                flag = 1;
            else
            {
                flag = 0;
                break;
            }
        }
        if (!flag)
        {
            printf("false\n");
            continue;
        }
        for (int i = 0; i < len; i++)
        {
            if (str[i] == ‘(‘ || str[i] == ‘{‘ || str[i] == ‘[‘)
            {
                s.push(str[i]);               //左括号就入栈
            }
            else if (str[i] == ‘)‘ || str[i] == ‘}‘ || str[i] == ‘]‘)            //如果是右括号，就看栈的顶端是否是和它配对的左括号
            {
                if (!s.empty())
                {
                    if (str[i] == ‘)‘)str[i] = ‘(‘;
                    else if (str[i] == ‘}‘)str[i] = ‘{‘;
                    else if (str[i] == ‘]‘)str[i] = ‘[‘;
                    if (s.top() == str[i])
                    {
                        s.pop();                    //如果匹配的话，就把左括号pop掉
                    }
                }
                else
                {
                    flag = 0;
                    break;
                }
            }
        }
        if (s.size())flag = 0;
        if (!flag)printf("false\n");
        else
            printf("true\n");
    }
    return 0;
}