<p>Strings <code>s1</code> and <code>s2</code> are <code>k</code><strong>-similar</strong> (for some non-negative integer <code>k</code>) if we can swap the positions of two letters in <code>s1</code> exactly <code>k</code> times so that the resulting string equals <code>s2</code>.</p>

<p>Given two anagrams <code>s1</code> and <code>s2</code>, return the smallest <code>k</code> for which <code>s1</code> and <code>s2</code> are <code>k</code><strong>-similar</strong>.</p>

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

<pre>
<strong>Input:</strong> s1 = &quot;ab&quot;, s2 = &quot;ba&quot;
<strong>Output:</strong> 1
<strong>Explanation:</strong> The two string are 1-similar because we can use one swap to change s1 to s2: &quot;ab&quot; --&gt; &quot;ba&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s1 = &quot;abc&quot;, s2 = &quot;bca&quot;
<strong>Output:</strong> 2
<strong>Explanation:</strong> The two strings are 2-similar because we can use two swaps to change s1 to s2: &quot;abc&quot; --&gt; &quot;bac&quot; --&gt; &quot;bca&quot;.
</pre>

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

<ul>
	<li><code>1 &lt;= s1.length &lt;= 20</code></li>
	<li><code>s2.length == s1.length</code></li>
	<li><code>s1</code> and <code>s2</code> contain only lowercase letters from the set <code>{&#39;a&#39;, &#39;b&#39;, &#39;c&#39;, &#39;d&#39;, &#39;e&#39;, &#39;f&#39;}</code>.</li>
	<li><code>s2</code> is an anagram of <code>s1</code>.</li>
</ul>

class Solution {
public:
    int dp1(string& a,string& b,int i){
        if(i==a.size()){
            return 0;
        }
        if(a[i]==b[i]){
            return dp1(a,b,i+1);
        }
        bool c=0;
        int cnt=a.size();
        for(int j=i+1;j<a.size();j++){
            if(a[j]==b[i]){
                swap(a[i],a[j]);
                cnt=min(cnt,1+dp1(a,b,i+1));
                swap(a[i],a[j]);
            }
        }
        return cnt;
    }
    int kSimilarity(string s1, string s2) {
        queue<pair<string,int>>q;
        unordered_set<string>s;
        q.push({s1,0});
        s.insert(s1);
        while(q.size()){
            auto y=q.front();
            q.pop();
            // cout<<y.first<<" "<<y.second<<endl;
            if(y.first==s2){
                return y.second;
            }
            for(int i=0;i<y.first.size();i++){
                if(y.first[i]!=s2[i]){
                    for(int j=i+1;j<y.first.size();j++){
                        if(s2[i]==y.first[j]){
                            swap(y.first[i],y.first[j]);
                            if(s.find(y.first)==s.end()){
                                s.insert(y.first);
                                q.push({y.first,y.second+1});
                            }
                            swap(y.first[i],y.first[j]);
                        }
                    }
                    break;
                }
            }

        }
        return 0;
        
    }
};
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