<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 helper(int index,string &s1,string &s2,unordered_map<string,unordered_map<int,int>>&dp){
        if(index==s1.length()) return 0;
        if(s1==s2) return 0;
        int mini=INT_MAX;
        if(dp[s2][index]!=0){
            return dp[s2][index];
        }

        if(s1[index]==s2[index]){
            return helper(index+1,s1,s2,dp);
        }
        else{
            
            for(int i=index+1;i<s2.length();i++){
                if(s1[index]==s2[i]){
                    swap(s2[i],s2[index]);
                    mini=min(mini,helper(index+1,s1,s2,dp)+1);
                    swap(s2[i],s2[index]);
                    //return mini;
                }
            }
        }

        return dp[s2][index]= mini;
    }

    int kSimilarity(string s1, string s2) {
        unordered_map<string,unordered_map<int,int>>dp;
        int ans=helper(0,s1,s2,dp);
        return ans;
    }
};
113691