Longest Substring with At Most K Distinct Characters

Given a string, find the length of the longest substring T that contains at most k distinct characters.

Example 1:

Input: s = "eceba", k = 2
Output: 3
Explanation: T is "ece" which its length is 3.

Example 2:

Input: s = "aa", k = 1
Output: 2
Explanation: T is "aa" which its length is 2.

class Solution {
public:
    int lengthOfLongestSubstringKDistinct(string s, int k) {
        vector<pair<char, int>> temp;
        int ans = 0;
        if (s.size() == 0 || k == 0) {
            return ans;
        }
        if (s.size() == 1) {
            return 1;
        }
       
        int count = 1;
        for (int i = 1; i < s.size(); i++) {
            if (s[i] == s[i - 1] ) {
                count++;
            } else {
                temp.push_back(make_pair(s[i-1], count));
                count = 1;
            }
        }
        temp.push_back(make_pair(s[s.size() - 1], count));
        int start = 0, end = 0;
        int kSum = 0;
        map<char, int> mp;
        while (end < temp.size()) {
            mp[temp[end].first] += temp[end].second;
            kSum += temp[end].second;
            while (mp.size() > k) {
                mp[temp[start].first] -= temp[start].second;
                kSum -= temp[start].second;
                if (mp[temp[start].first] == 0) {
                    mp.erase(temp[start].first);
                }
                start++;
            }
            ans = max(ans, kSum);
            end++;
        }
        return ans;
    }
};

============== Efficient one ======

int lengthOfLongestSubstringKDistinct(string s, int k) {
        int res = 0, left = 0;
        unordered_map<char, int> m;
        for (int i = 0; i < s.size(); ++i) {
            ++m[s[i]];
            while (m.size() > k) {
                if (--m[s[left]] == 0) m.erase(s[left]);
                ++left;
            }
            res = max(res, i - left + 1);
        }
        return res;
    }