#include <iostream>class DisjointSet{
public:DisjointSet(int size):parent(size,-1){}void Union(int x, int y){int root1=Find(x), root2=Find(y);if (root1==root2) return;// whoever's size is bigger becomes parent of other// notice parent[root] is negative, if parent[root] is smaller, then its size is largerif (parent[root1]>parent[root2]){parent[root2] += parent[root1];parent[root1] = root2;}else{parent[root1] += parent[root2];parent[root2] = root1;}}int Find(int x){if (parent[x]<0) return x;return parent[x] = Find(parent[x]);}private:vector<int> parent;
};int main() {DisjointSet s(10);s.Union(2,1);cout << s.Find(1);return 0;
}

#include <iostream>struct Node{int val;Node *parent;int rank;Node(int v):val(v),parent(this),rank(0){}
};class DisjointSet{
public:// Create a set with only one elementvoid makeSet(int val){Node *node=new Node(val);m[val] = node;}// Combines two sets, unions by rankvoid unionSet(int val1, int val2){Node *node1=m[val1];Node *node2=m[val2];Node *root1=findSet(node1);Node *root2=findSet(node2);// they of part of the same set, do nothingif (root1==root2) return;// whoever's rank is higher becomes parent of otherif (root1->rank > root2->rank)root2->parent = root1;else if (root1->rank < root2->rank)root1->parent = root2->parent;else{root1->rank += 1;root2->parent = root1;}}int findSet(int val){return findSet(m[val])->val;}// Find the representative recursively and does path compression as wellNode *findSet(Node *node){Node *parent=node->parent;if (parent==node) return node;node->parent = findSet(node->parent);return node->parent;}private:unordered_map<int,Node *> m; // node val -> Node *
};int main(){DisjointSet a;for (int i=1;i<=7;++i) a.makeSet(i);a.unionSet(1,2);a.unionSet(2,3);cout << a.findSet(1) << endl;cout << a.findSet(3) << endl;cout << a.findSet(7) << endl;return 0;
}