Leetcode: Valid Parentheses (0ms)(string)(stack)

PROBLEM:
https://leetcode.com/problems/valid-parentheses/

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1. using stack to temporally store the characters;
2. when meet [, {, (, push to stack;
3. when meet }, ], ), compare with the top of stack;
        if it's a pair, pop the top one (delete the top one);
        if it's not a pair, it's failed. 
4. if in the final, nothing it's left, it's true. 

See codes for details. 



/////////////////////////////////////////////////////////
// codes 0ms

class Solution {

public:

       bool isValid(string s) {

              stack<char> sta;

              sta.push('0');

              for (auto c : s){

                     switch (c) {

                     case '{':

                           sta.push('{');

                           break;

                     case '}':

                           if (sta.top() != '{') return false;

                           else sta.pop();

                           break;

                     case '[':

                           sta.push('[');

                           break;

                     case ']':

                           if (sta.top() != '[') return false;

                           else sta.pop();

                           break;

                     case '(':

                           sta.push('(');

                           break;

                     case ')':

                           if (sta.top() != '(') return false;

                           else sta.pop();

                           break;

                     default:;

                     }

              }

              if (sta.top() == '0')return true;

              else return false;

       }

};