<p>You are given a string <code>s</code> and an integer <code>k</code>. You can choose any character of the string and change it to any other uppercase English character. You can perform this operation at most <code>k</code> times.</p>

<p>Return <em>the length of the longest substring containing the same letter you can get after performing the above operations</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;ABAB&quot;, k = 2
<strong>Output:</strong> 4
<strong>Explanation:</strong> Replace the two &#39;A&#39;s with two &#39;B&#39;s or vice versa.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;AABABBA&quot;, k = 1
<strong>Output:</strong> 4
<strong>Explanation:</strong> Replace the one &#39;A&#39; in the middle with &#39;B&#39; and form &quot;AABBBBA&quot;.
The substring &quot;BBBB&quot; has the longest repeating letters, which is 4.
There may exists other ways to achieve this answer too.</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
	<li><code>s</code> consists of only uppercase English letters.</li>
	<li><code>0 &lt;= k &lt;= s.length</code></li>
</ul>

class Solution {
public:
    int characterReplacement(string s, int k) {
        int n = s.size();
        int maxi = 1;
        
        map<char,int> mp;
        int l = 0 , r = 0;
        while(r < n){
            mp[s[r]]++;
            int len = r - l + 1;
            int maxfreq = 1;
            for(auto i : mp){
                if(i.second > maxfreq){
                    maxfreq = i.second;
                }
            }
            if(len - maxfreq <= k) maxi = max(maxi,len);
            else{
                mp[s[l]]--;
                if(mp[s[l]] == 0) mp.erase(s[l]);
                l++;
            }
            r++;
        }
        return maxi;
    }
};
10600