<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>

from collections import Counter


class DSU:

    def __init__(self, word):
        self.parent = list(range(len(word)))
        self.sorted_words = [Counter([char]) for char in word]

    def _parent(self, u):
        if self.parent[u] == u:
            return u
        self.parent[u] = self._parent(self.parent[u])
        return self.parent[u]

    def unite(self, u, v):
        parent_u = self._parent(u)
        parent_v = self._parent(v)
        if parent_u != parent_v:
            if len(self.sorted_words[parent_u]) < len(self.sorted_words[parent_v]):
                parent_u, parent_v = parent_v, parent_u
            self.parent[parent_v] = parent_u
            self.sorted_words[parent_u] += self.sorted_words[parent_v]
            self.sorted_words[parent_v] = Counter()

    def sort_words(self):
        for index, char_list in enumerate(self.sorted_words):
            sorted_values = sorted(char_list.items())
            self.sorted_words[index] = []
            for char, freq in sorted_values:
                while freq:
                    self.sorted_words[index].append(char)
                    freq -= 1

    def get_char(self, index):
        parent_index = self._parent(index)
        return self.sorted_words[parent_index].pop()


class Solution:
    def smallestStringWithSwaps(self, s: str, pairs: List[List[int]]) -> str:
        dsu = DSU(s)
        for a, b in pairs:
            dsu.unite(a, b)
        dsu.sort_words()
        result = []
        for index in range(len(s) - 1, -1, -1):
            result.append(dsu.get_char(index))
        return ''.join(result[ : : -1])
680