Today I have done leetcode's April LeetCoding Challenge with cpp.

April LeetCoding Challenge 10

Description

Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.
3. Every close bracket has a corresponding open bracket of the same type.

Example 1:

Input: s = "()"
Output: true

Example 2:

Input: s = "()[]{}"
Output: true

Example 3:

Input: s = "(]"
Output: false

Constraints:

• 1 <= s.length <= 104
• s consists of parentheses only '()[]{}'.

Solution

class Solution {
public:
  bool isValid(string s) {
    vector<char> st;
    for(auto c : s) {
      switch(c) {
        case '(':
        case '[':
        case '{':
          st.push_back(c);
          break;
        case ')':
          if(st.empty() || st.back() != '(') {
            return false;
          }
          st.pop_back();
          break;
        case ']':
          if(st.empty() || st.back() != '[') {
            return false;
          }
          st.pop_back();
          break;
        case '}':
          if(st.empty() || st.back() != '{') {
            return false;
          }
          st.pop_back();
          break;
        default:
          return false;
      }
    }
    return st.empty();
  }
};

// Accepted
// 93/93 cases passed (2 ms)
// Your runtime beats 46.33 % of cpp submissions
// Your memory usage beats 56.25 % of cpp submissions (6.4 MB)