<p>You are given a string <code>s</code>, and an array of pairs of indices in the string&nbsp;<code>pairs</code>&nbsp;where&nbsp;<code>pairs[i] =&nbsp;[a, b]</code>&nbsp;indicates 2 indices(0-indexed) of the string.</p>

<p>You can&nbsp;swap the characters at any pair of indices in the given&nbsp;<code>pairs</code>&nbsp;<strong>any number of times</strong>.</p>

<p>Return the&nbsp;lexicographically smallest string that <code>s</code>&nbsp;can be changed to after using the swaps.</p>

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

<pre>
<strong>Input:</strong> s = &quot;dcab&quot;, pairs = [[0,3],[1,2]]
<strong>Output:</strong> &quot;bacd&quot;
<strong>Explaination:</strong> 
Swap s[0] and s[3], s = &quot;bcad&quot;
Swap s[1] and s[2], s = &quot;bacd&quot;
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;dcab&quot;, pairs = [[0,3],[1,2],[0,2]]
<strong>Output:</strong> &quot;abcd&quot;
<strong>Explaination: </strong>
Swap s[0] and s[3], s = &quot;bcad&quot;
Swap s[0] and s[2], s = &quot;acbd&quot;
Swap s[1] and s[2], s = &quot;abcd&quot;</pre>

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

<pre>
<strong>Input:</strong> s = &quot;cba&quot;, pairs = [[0,1],[1,2]]
<strong>Output:</strong> &quot;abc&quot;
<strong>Explaination: </strong>
Swap s[0] and s[1], s = &quot;bca&quot;
Swap s[1] and s[2], s = &quot;bac&quot;
Swap s[0] and s[1], s = &quot;abc&quot;
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 10^5</code></li>
	<li><code>0 &lt;= pairs.length &lt;= 10^5</code></li>
	<li><code>0 &lt;= pairs[i][0], pairs[i][1] &lt;&nbsp;s.length</code></li>
	<li><code>s</code>&nbsp;only contains lower case English letters.</li>
</ul>

class Solution:
    def __init__(self):
        self.adj = defaultdict(list)
        self.visited = [False] * 100001

    def smallestStringWithSwaps(self, s: str, pairs: List[List[int]]) -> str:
        if not pairs:
            return s

        s_len = len(s)

        # build undirected graph self.adj list
        for src, dest in pairs:
            self.adj[src].append(dest)
            self.adj[dest].append(src)

        result = list(s)
        for vertex in range(s_len):
            if self.visited[vertex]:
                continue

            chars, indices = [], []

            self.dfs(result, vertex, chars, indices)
            
            chars = sorted(chars)
            indices = sorted(indices)

            for i in range(len(chars)):
                result[indices[i]] = chars[i]

        return ''.join(result)

    def dfs(self, s: List[str], vertex: int, chars: List[str], indices: List[int]):
        # Add char and index to lists
        chars.append(s[vertex])
        indices.append(vertex)

        self.visited[vertex] = True

        for adjacent in self.adj[vertex]:
            if not self.visited[adjacent]:
                self.dfs(s, adjacent, chars, indices) 
        
523