20. Valid Parentheses

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

给定一个只含括号的字符串，判断字符串是否匹配

class Solution {
public:
    bool isValid(string s) {
        stack<char> stk;
        for(int i=0; i<s.size(); ++i)
        {
            switch(s[i])
            {
                case ')':
                    if(!stk.empty() && stk.top()=='(')
                        stk.pop();
                    else
                        return false;
                    break;
                
                case ']':
                    if(!stk.empty() && stk.top()=='[')
                        stk.pop();
                    else
                        return false;
                    break;
                
                case '}':
                    if(!stk.empty() && stk.top()=='{')
                        stk.pop();
                    else
                        return false;
                    break;
                
                default:
                    stk.push(s[i]);
            }
        }
            if(!stk.empty())
                return false;
            else
                return true;
        }
};

结果：

Runtime: 0 ms, faster than 100.00% of C++ online submissions for Valid Parentheses.
Memory Usage: 6.2 MB, less than 100.00% of C++ online submissions for Valid Parentheses.