[LeetCode 解题报告]020.Valid Parentheses

版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。

本文链接： https://blog.csdn.net/caicaiatnbu/article/details/102733798

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.

Note that an empty string is also considered valid.

Example 1:

Input: "()"
Output: true

Example 2:

Input: "()[]{}"
Output: true

Example 3:

Input: "(]"
Output: false

Example 4:

Input: "([)]"
Output: false

Example 5:

Input: "{[]}"
Output: true

 考察：栈的基本使用

class Solution {
public:
    bool isValid(string s) {
        stack<char> ss;
        for (int i = 0; i < s.length(); i ++) {
            if (s[i] == '(' || s[i] == '[' || s[i] =='{')
                ss.push(s[i]);
            else {
                if(ss.empty())
                    return false;
                if((ss.top() == '(' && s[i] == ')') || (ss.top() == '[' && s[i] == ']') || (ss.top() == '{' && s[i] == '}'))
                    ss.pop();
                else
                    return false;
            }
        }
        return ss.empty();
    }
};

完，