<p>There are <code>n</code> couples sitting in <code>2n</code> seats arranged in a row and want to hold hands.</p>

<p>The people and seats are represented by an integer array <code>row</code> where <code>row[i]</code> is the ID of the person sitting in the <code>i<sup>th</sup></code> seat. The couples are numbered in order, the first couple being <code>(0, 1)</code>, the second couple being <code>(2, 3)</code>, and so on with the last couple being <code>(2n - 2, 2n - 1)</code>.</p>

<p>Return <em>the minimum number of swaps so that every couple is sitting side by side</em>. A swap consists of choosing any two people, then they stand up and switch seats.</p>

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

<pre>
<strong>Input:</strong> row = [0,2,1,3]
<strong>Output:</strong> 1
<strong>Explanation:</strong> We only need to swap the second (row[1]) and third (row[2]) person.
</pre>

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

<pre>
<strong>Input:</strong> row = [3,2,0,1]
<strong>Output:</strong> 0
<strong>Explanation:</strong> All couples are already seated side by side.
</pre>

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

<ul>
	<li><code>2n == row.length</code></li>
	<li><code>2 &lt;= n &lt;= 30</code></li>
	<li><code>n</code> is even.</li>
	<li><code>0 &lt;= row[i] &lt; 2n</code></li>
	<li>All the elements of <code>row</code> are <strong>unique</strong>.</li>
</ul>

class DisjointSet{
    vector<int> parent;
    vector<int> size;
    int islands;
    public:
    DisjointSet(int n){
        parent.resize(n);
        for(int i=0;i<n;i++) parent[i]=i;
        size.resize(n,1);
        islands=n;
    }
    int ulpar(int u){
        if(parent[u]==u) return u;
        return parent[u]=ulpar(parent[u]);
    }
    void link(int u,int v){
        int pu=ulpar(u);
        int pv=ulpar(v);
        if(pu==pv) return;
        islands--;
        if(size[pu]>size[pv]){
            size[pu]+=size[pv];
            parent[pv]=pu;
        }
        else{
            size[pv]+=size[pu];
            parent[pu]=pv;
        }
    }
    int numislands(){
        return islands;
    }
};

class Solution {
public:
    int minSwapsCouples(vector<int>& row) {
        int n=row.size()/2;
        DisjointSet ds(n);
        for(int i=0;i<2*n;i=i+2){
            ds.link(row[i]/2,row[i+1]/2);
            cout<<row[i]<<","<<row[i+1]<<" "<<ds.numislands()<<endl;
        }
        return n-ds.numislands();
    }
};
9100