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

May LeetCoding Challenge 6

Description

Remove All Adjacent Duplicates in String II

You are given a string s and an integer k, a k duplicate removal consists of choosing k adjacent and equal letters from s and removing them, causing the left and the right side of the deleted substring to concatenate together.

We repeatedly make k duplicate removals on s until we no longer can.

Return the final string after all such duplicate removals have been made. It is guaranteed that the answer is unique.

Example 1:

Input: s = "abcd", k = 2
Output: "abcd"
Explanation: There's nothing to delete.

Example 2:

Input: s = "deeedbbcccbdaa", k = 3
Output: "aa"
Explanation: 
First delete "eee" and "ccc", get "ddbbbdaa"
Then delete "bbb", get "dddaa"
Finally delete "ddd", get "aa"

Example 3:

Input: s = "pbbcggttciiippooaais", k = 2
Output: "ps"

Constraints:

• 1 <= s.length <= 10^5
• 2 <= k <= 10^4
• s only contains lower case English letters.

Solution

class Solution {
public:
  string removeDuplicates(string s, int k) {
    vector<pair<char, int>> st;
    for(auto c : s) {
      if(st.empty() || st.back().first != c) {
        st.push_back(make_pair(c, 1));
      } else {
        st.back().second += 1;
        if(st.back().second == k) st.pop_back();
      }
    }
    string answer;
    for(auto [c, cnt] : st) {
      for(int i = 0; i < cnt; ++i) answer.push_back(c);
    }
    return answer;
  }
};

// Accepted
// 20/20 cases passed (25 ms)
// Your runtime beats 68.41 % of cpp submissions
// Your memory usage beats 54.02 % of cpp submissions (10.6 MB)