20.有效的括号

版权声明：孔庆鑫 https://blog.csdn.net/kongqingxin12/article/details/85336973

20.有效的括号

class Solution {
public:
    bool isValid(string s)
    {
        vector<char> last;
        for (int i = 0; i <s.length() ; ++i) {
           if(s[i]=='('||s[i]=='['||s[i]=='{')
               last.push_back(s[i]);
           else
           {
               if(last.empty())
                   return false;
               switch (s[i])
               {
                   case ')':
                       if(last.back()!='(')
                           return  false;
                       break;
                   case ']':
                       if(last.back()!='[')
                           return false;
                       break;
                   case '}':
                       if(last.back()!='{')
                           return false;
                       break;
               }
               last.pop_back();
           }
        }
        if(last.empty())
            return true;
        return false;
    }
};