LeetCode 20 Valid Parentheses

20. Valid Parentheses

Total Accepted: 102983 Total Submissions: 352605 Difficulty: Easy

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.

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Have you met this question in a real interview?

验证字符串括号是否配对合法。

经典问题了

用个栈就解决。

class Solution {
public:
    bool isValid(string s) 
    {
        int len=s.length();
        if(len%2)
            return false;
        stack<char> st;
        for(int i=0;i<len;i++)
        {
                if(!st.empty())
                {
                        if ((st.top()=='['&&s[i]==']')||(st.top()=='('&&s[i]==')')||(st.top()=='{'&&s[i]=='}'))
                                st.pop();
                        else
                                st.push(s[i]);
                }
                else
                {
                        st.push(s[i]);
                }
        }
        return st.empty();
    }
};