<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 {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        string ans(s.size(), '*');

        UnionFind uF(s.size());
        for(auto pair : pairs) {
            uF.unionSet(pair[0], pair[1]);
        }

        for(auto u : uF.getUnions()) {
            string tmp;
            for(auto i : u.second) {
                tmp += s[i];
            }
            sort(tmp.begin(), tmp.end());
            
            int j = 0;
            for(auto i : u.second) {
                ans[i] = tmp[j++];
            }
        }

        return ans;
    }

private:
    class UnionFind {
    public:
        UnionFind(int sz) : root(sz), rank(sz, 1) {
            for(int i=0; i<sz; i++) {
                root[i] = i;
            }
        }

        int find(int x) {
            if(x == root[x]) {
                return x;
            }
            return root[x] = find(root[x]);
        }

        void unionSet(int x, int y) {
            int rootX = find(x);
            int rootY = find(y);
            if(rootX == rootY) return;
            if(rank[rootX] > rank[rootY]) {
                root[rootY] = rootX;
            }
            else if(rank[rootX] < rank[rootY]) {
                root[rootX] = rootY;
            }
            else {
                root[rootX] = rootY;
                rank[rootY]++;
            }
        }

        unordered_map<int, vector<int>> getUnions() {
            if(unions.size()) return unions;
            for(int i=0; i<root.size(); i++) {
                find(i);
                unions[root[i]].push_back(i);
            }
            return unions;
        }

    private:
        vector<int> root;
        vector<int> rank;
        unordered_map<int, vector<int>> unions;
    };
};
61587