<p>Given a string <code>s</code> and an integer <code>k</code>, return <em>the maximum number of vowel letters in any substring of </em><code>s</code><em> with length </em><code>k</code>.</p>

<p><strong>Vowel letters</strong> in English are <code>&#39;a&#39;</code>, <code>&#39;e&#39;</code>, <code>&#39;i&#39;</code>, <code>&#39;o&#39;</code>, and <code>&#39;u&#39;</code>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;abciiidef&quot;, k = 3
<strong>Output:</strong> 3
<strong>Explanation:</strong> The substring &quot;iii&quot; contains 3 vowel letters.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;aeiou&quot;, k = 2
<strong>Output:</strong> 2
<strong>Explanation:</strong> Any substring of length 2 contains 2 vowels.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;leetcode&quot;, k = 3
<strong>Output:</strong> 2
<strong>Explanation:</strong> &quot;lee&quot;, &quot;eet&quot; and &quot;ode&quot; contain 2 vowels.
</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 lowercase English letters.</li>
	<li><code>1 &lt;= k &lt;= s.length</code></li>
</ul>

class Solution {
public:
    bool check(char ch){
        if(ch == 'a'|| ch == 'e'|| ch == 'i' || ch == 'o' || ch == 'u'){
            return true;
        }
        return false;
    }
    int checkMax(unordered_map<char,int>&mp){
        int sum = 0;
        for(auto &it : mp){
            sum += it.second;
        }
        return sum;
    }
    int maxVowels(string s, int k) {
        unordered_map<char,int> mp;
        int l = 0, r = 0, maxVowels = 0, n = s.length();
        while(r < n){
            char ch = s[r];
            int len = r - l + 1;
            if(check(ch)){
                    mp[s[r]]++;
            }
            if(len > k){    
                if(check(s[l])){
                    mp[s[l]]--;
                    if (mp[s[l]] == 0) {
                        mp.erase(s[l]);
                    }
                }
                l++;
            }
            maxVowels = max(maxVowels,checkMax(mp));
            r++;
        }
        return maxVowels;
    }
};
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