20.Valid Parentheses (Stack)-优快云博客

本文介绍了一种使用栈解决括号匹配问题的有效方法。通过遍历输入字符串并将括号压入或弹出栈来检查括号是否正确配对，确保括号顺序正确。

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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.

思路：与括号相关的问题，通常用栈来处理。需要考虑的是将什么信息入栈。本题将括号的类型入栈，在Longest Valid Parentheses中，是将左括号的位置入栈

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