LeetCode: Valid Parentheses

一次过

class Solution {
public:
    bool isValid(string s) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        stack<char> S;
        for (int i = 0; i < s.size(); i++) {
            if (s[i] == '(' || s[i] == '[' || s[i] == '{') S.push(s[i]);
            else {
                if (S.empty()) return false;
                char tmp = S.top();
                if (s[i] == ')') {
                    if (tmp == '(') S.pop();
                    else return false;
                }
                if (s[i] == ']') {
                    if (tmp == '[') S.pop();
                    else return false;
                }
                if (s[i] == '}') {
                    if (tmp == '{') S.pop();
                    else return false;
                }
            }
        }
        if (S.empty()) return true;
        else return false;
    }
};

 C#

public class Solution {
    public bool IsValid(string s) {
        Stack<char> S = new Stack<char>();
        for (int i = 0; i < s.Length; i++) {
            if (s[i] == '(' || s[i] == '[' || s[i] == '{') S.Push(s[i]);
            else {
                if (S.Count == 0) return false;
                char peek = S.Peek();
                if (s[i] == ')') {
                    if (peek == '(') S.Pop();
                    else return false;
                }
                if (s[i] == ']') {
                    if (peek == '[') S.Pop();
                    else return false;
                }
                if (s[i] == '}') {
                    if (peek == '{') S.Pop();
                    else return false;
                }
            }
        }
        return S.Count == 0;
    }
}