Leetcode 20. Valid Parentheses

Tyan

发布于 2019-05-25 22:46:43

2990

发布于 2019-05-25 22:46:43

文章被收录于专栏：SnailTyanSnailTyan

文章作者：Tyan

博客：noahsnail.com | CSDN | 简书

1. Description

2. Solution

Version 1

class Solution {
public:
    bool isValid(string s) {
        stack<char> st;
        for(char ch : s) {
            if(st.empty()) {
                st.push(ch);
            }
            else {
                if((ch == ')' && st.top() == '(') || (ch == ']' && st.top() == '[') || (ch == '}' && st.top() == '{')) {
                    st.pop();
                }
                else {
                    st.push(ch);
                }
            }
        }
        return st.empty();
    }
};

Version 2

class Solution {
public:
    bool isValid(string s) {
        stack<char> st;
        for(char ch : s) {
            if(st.empty()) {
                st.push(ch);
            }
            else {
                if((ch == ')' && st.top() != '(') || (ch == ']' && st.top() != '[') || (ch == '}' && st.top() != '{')) {
                    return false;
                }
                else if(ch == ')' || ch == ']' || ch == '}'){
                    st.pop();
                }
                else {
                    st.push(ch);
                }
            }
        }
        return st.empty();
    }
};