LeetCode: Valid Parentheses

一次过

 1 class Solution {
 2 public:
 3     bool isValid(string s) {
 4         // Start typing your C/C++ solution below
 5         // DO NOT write int main() function
 6         stack<char> S;
 7         for (int i = 0; i < s.size(); i++) {
 8             if (s[i] == '(' || s[i] == '[' || s[i] == '{') S.push(s[i]);
 9             else {
10                 if (S.empty()) return false;
11                 char tmp = S.top();
12                 if (s[i] == ')') {
13                     if (tmp == '(') S.pop();
14                     else return false;
15                 }
16                 if (s[i] == ']') {
17                     if (tmp == '[') S.pop();
18                     else return false;
19                 }
20                 if (s[i] == '}') {
21                     if (tmp == '{') S.pop();
22                     else return false;
23                 }
24             }
25         }
26         if (S.empty()) return true;
27         else return false;
28     }
29 };

 1 public class Solution {
 2     public bool IsValid(string s) {
 3         Stack<char> S = new Stack<char>();
 4         for (int i = 0; i < s.Length; i++) {
 5             if (s[i] == '(' || s[i] == '[' || s[i] == '{') S.Push(s[i]);
 6             else {
 7                 if (S.Count == 0) return false;
 8                 char peek = S.Peek();
 9                 if (s[i] == ')') {
10                     if (peek == '(') S.Pop();
11                     else return false;
12                 }
13                 if (s[i] == ']') {
14                     if (peek == '[') S.Pop();
15                     else return false;
16                 }
17                 if (s[i] == '}') {
18                     if (peek == '{') S.Pop();
19                     else return false;
20                 }
21             }
22         }
23         return S.Count == 0;
24     }
25 }

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