<p>You are given two strings <code>s1</code> and <code>s2</code> of equal length. A <strong>string swap</strong> is an operation where you choose two indices in a string (not necessarily different) and swap the characters at these indices.</p>

<p>Return <code>true</code> <em>if it is possible to make both strings equal by performing <strong>at most one string swap </strong>on <strong>exactly one</strong> of the strings. </em>Otherwise, return <code>false</code>.</p>

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

<pre>
<strong>Input:</strong> s1 = &quot;bank&quot;, s2 = &quot;kanb&quot;
<strong>Output:</strong> true
<strong>Explanation:</strong> For example, swap the first character with the last character of s2 to make &quot;bank&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s1 = &quot;attack&quot;, s2 = &quot;defend&quot;
<strong>Output:</strong> false
<strong>Explanation:</strong> It is impossible to make them equal with one string swap.
</pre>

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

<pre>
<strong>Input:</strong> s1 = &quot;kelb&quot;, s2 = &quot;kelb&quot;
<strong>Output:</strong> true
<strong>Explanation:</strong> The two strings are already equal, so no string swap operation is required.
</pre>

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

<ul>
	<li><code>1 &lt;= s1.length, s2.length &lt;= 100</code></li>
	<li><code>s1.length == s2.length</code></li>
	<li><code>s1</code> and <code>s2</code> consist of only lowercase English letters.</li>
</ul>

class Solution:
    def areAlmostEqual(self, s: str, goal: str) -> bool:
        if len(s)!=len(goal):
            return False
        if s==goal:
            return True
        pairs=[]
        dups=False
        seen=set()
        for i in range(len(goal)):
            if goal[i] in seen:
                dups=True
            seen.add(goal[i])
            if s[i]!=goal[i]:
                pairs.append((s[i],goal[i]))
        if len(pairs)!=2:
            return False
        return pairs[0][0]==pairs[1][1] and pairs[1][0]==pairs[0][1]

                
16500