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LeetCode: Valid Parentheses [020]

【题目】

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.


【题意】

 判断给定的字符串是否是合法的成对括号串


【思路】


【代码】

class Solution {
public:
    bool isPair(char left, char right){
        if(left==‘(‘&&right==‘)‘)return true;
        if(left==‘{‘&&right==‘}‘)return true;
        if(left==‘[‘&&right==‘]‘)return true;
        return false;
    }
    bool isValid(string s) {
        stack<int>st;
        for(int i=0; i<s.length(); i++){
            if(st.empty())st.push(s[i]);
            else{
                char left=st.top();
                if(isPair(left,s[i]))st.pop();
                else st.push(s[i]);
            }
        }
        return st.empty();
    }
};