LeetCode 020 Valid Parentheses

题目描述：Valid Parentheses

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：

栈

代码如下：

class Solution {
public:
    bool isValid(string s) {

        string left = "([{";
        string right = ")]}";
        stack<char> stk;

        for(auto c : s){

            //如果是"([{"，则压入栈中
            if(left.find(c) != string::npos){
                stk.push(c);
            }
            //如果不是"([{"，则匹配
            else{
                if(stk.empty() || stk.top() != left[right.find(c)])
                    return false;
                else stk.pop();
            }
        }

        return stk.empty();

    }
};