<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 DisjointSet {
      public: 
      vector<int> parent, size;
      DisjointSet(int n){
           parent.resize(n+1);
           size.resize(n+1);

           for (int i=0;i<=n;i++){
               parent[i] = i;
               size[i] = 1;
           }
      }

      int findUpar(int node){
        if (parent[node] == node) return node;

        return parent[node] = findUpar(parent[node]);
    }

      void unionBySize(int u, int v){
           int ulp_u = findUpar(u);
           int ulp_v = findUpar(v);
           if (ulp_u == ulp_v) return ;

           if (size[ulp_u] < size[ulp_v]){
               size[ulp_v] += size[ulp_u];
               parent[ulp_u] = ulp_v; 
           } else {
               size[ulp_u] += size[ulp_v];
               parent[ulp_v] = ulp_u; 
           }
      }
};
class Solution {
public:
    string smallestStringWithSwaps(string s, vector<vector<int>>& pairs) {
        int n = s.length();
        DisjointSet ds(n);
        unordered_map<int, vector<pair<char, int>>> adj;

        for (auto x: pairs){
            int u = x[0], v = x[1];
            ds.unionBySize(u, v);
        }

        vector<int> vis(n, 0);
        for (int i=0;i<n;i++){
           if (vis[i] == 0){
               int ulp = ds.findUpar(i);
               adj[ulp].push_back({s[i], i});
           }
        }
        
        vector<vector<pair<char, int>>> res;
       for (auto x: adj){
           vector<pair<char, int>> arr = x.second;
           sort(arr.begin(), arr.end());
           vector<int> indices;
           for (int i=0;i<arr.size();i++){
             indices.push_back(arr[i].second);
           }
           sort(indices.begin(), indices.end());

           for (int i=0;i<arr.size();i++){
            arr[i].second = indices[i];
           }
           res.push_back(arr);
       }

       vector<char> result(n);
       for (int i=0;i<res.size();i++){
        for (int j=0;j<res[i].size();j++){
            char ch = res[i][j].first;
            int ind = res[i][j].second;
            result[ind] = ch;
        }
       }
       
       string str = "";
       for (auto x: result){
        str += x;
       }
       return str;
    }
};
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