<p>Given two strings <code>s1</code> and <code>s2</code>, return <code>true</code><em> if </em><code>s2</code><em> contains a permutation of </em><code>s1</code><em>, or </em><code>false</code><em> otherwise</em>.</p>

<p>In other words, return <code>true</code> if one of <code>s1</code>&#39;s permutations is the substring of <code>s2</code>.</p>

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

<pre>
<strong>Input:</strong> s1 = &quot;ab&quot;, s2 = &quot;eidbaooo&quot;
<strong>Output:</strong> true
<strong>Explanation:</strong> s2 contains one permutation of s1 (&quot;ba&quot;).
</pre>

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

<pre>
<strong>Input:</strong> s1 = &quot;ab&quot;, s2 = &quot;eidboaoo&quot;
<strong>Output:</strong> false
</pre>

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

<ul>
	<li><code>1 &lt;= s1.length, s2.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s1</code> and <code>s2</code> consist of lowercase English letters.</li>
</ul>

class Solution {
public:
    bool ifEqual(vector<int>v1, vector<int>v2){
        if(v1.size()!=v2.size())
            return false;
        for(int i=0; i<v1.size(); i++){
            if(v1[i]!=v2[i])
                return false;
        }
        
        return true;
    }
    
    bool checkInclusion(string s1, string s2) {
        int winSize = s1.length();
        vector<int>v(26,0);
        for(int i=0; i<s1.length(); i++){
            v[s1[i]-'a']++;
        }
        
        int s=0;
        for(int i=0; i<s2.length(); i++){
            vector<int>v2(26,0);
            for(int j=0; j<s1.length(); j++){
                if(s+j<s2.length())
                    v2[s2[s+j]-'a']++;
            }
            
            if(ifEqual(v2,v)){
                return true;
            }
            else{
                s++;
            }
        }
        
        return false;
    }
};
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