Valid Parentheses

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