20 Valid Parentheses

链接：https://leetcode.com/problems/valid-parentheses/
问题描述：
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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Hide Similar Problems (M) Generate Parentheses (H) Longest Valid Parentheses

求小括号，中括号，大括号是否对称使用。

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

          }
        }
        return m.empty();
    }
};