<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 Solution {
    int par[30], size[30];
    int N;
public:
    int minSwapsCouples(vector<int>& row) {
        int n_2 = row.size();
        int n = n_2/2;
        for(int i=0; i<n; i++){
            par[i]=i;
            size[i]=1;
        }
        N=n;


        for(int i=0; i<2*n; i+=2){
            int seat1 = row[i]/2;
            int seat2 = row[i+1]/2;

            Union(seat1, seat2);
            
            // cout<<seat1<<" "<<seat2<<endl;
        }

        int comp = components();
        // cout<<comp<<endl;

        int ans = n - comp;
        return ans;
    }

    int find(int u){
        if(par[u]==u)return u;
        return par[u]=find(par[u]);
    }

    void Union(int u, int v){
        int pu = find(u);
        int pv = find(v);

        if(pu!=pv){
            if(size[pu]<size[pv]){
                par[pu]=pv;
                size[pv]+=size[pu];
            }
            else{
                par[pv]=pu;
                size[pu]+=size[pv];
            }
        }
    }

    int components(){
        int ans = 0;
        for(int i=0; i<N; i++){
            if(par[i]==i)ans++;
        }

        return ans;
    }
};
9000