Valid Parentheses

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Description:

Given a string containing just the characters ’(’, ’)’, ’{’, ’}’, ’[’ and ’]’, determine if the
input string is valid.
The brackets must close in the correct order, ”()” and ”()[]” are all valid but ”(]” and ”([)]” are
not.

分析：
使用栈

代码：

#include <iostream>#include <string>#include <stack>#include <algorithm>using namespace std;bool ValidParentTheses(string str){    int  len = str.size();    string leftBracket = "([{";    string rightBracket = ")]}";    stack<char> sk;    for (int i = 0; i < len; i++)    {        if (leftBracket.find(str[i]) != string::npos)        {            sk.push(str[i]);        }        if (rightBracket.find(str[i]) != string::npos)        {            if (!sk.empty() && sk.top() == leftBracket[rightBracket.find(str[i])])            {                sk.pop();            }            else                return false;        }    }    if (!sk.empty())        return false;    return true;}int main(){    string str = "()";    string str2 = "()[]";    string str3 = "(]";    string str4 = "([)]";    cout << boolalpha << ValidParentTheses(str) << endl;    cout << boolalpha << ValidParentTheses(str2) << endl;    cout << boolalpha << ValidParentTheses(str3) << endl;    cout << boolalpha << ValidParentTheses(str4) << endl;    system("pause");    return 0;}

测试：

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