• 19.1.29 [LeetCode 20] Valid Parentheses


    Given a string containing just the characters '('')''{''}''[' and ']', determine if the input string is valid.

    An input string is valid if:

    1. Open brackets must be closed by the same type of brackets.
    2. Open brackets must be closed in the correct order.

    Note that an empty string is also considered valid.

    Example 1:

    Input: "()"
    Output: true
    

    Example 2:

    Input: "()[]{}"
    Output: true
    

    Example 3:

    Input: "(]"
    Output: false
    

    Example 4:

    Input: "([)]"
    Output: false
    

    Example 5:

    Input: "{[]}"
    Output: true
     1 class Solution {
     2 public:
     3     bool isValid(string s) {
     4         stack<char>q;
     5         for (int i = 0; s[i]; i++) {
     6             if (s[i] == '(' || s[i] == '[' || s[i] == '{')
     7                 q.push(s[i]);
     8             else if (s[i] == ')'||s[i]==']'||s[i]=='}') {
     9                 if (q.empty())return false;
    10                 char c = q.top();
    11                 if (s[i] == ')') {
    12                     if (c == '(')q.pop();
    13                     else
    14                         return false;
    15                 }
    16                 else if (s[i] == ']') {
    17                     if (c == '[')q.pop();
    18                     else
    19                         return false;
    20                 }
    21                 else if (s[i] == '}') {
    22                     if (c == '{')q.pop();
    23                     else
    24                         return false;
    25                 }
    26             }
    27         }
    28         if (!q.empty())return false;
    29         return true;
    30     }
    31 };
    View Code
    注定失败的战争,也要拼尽全力去打赢它; 就算输,也要输得足够漂亮。
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  • 原文地址:https://www.cnblogs.com/yalphait/p/10333470.html
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