OJ刷题记录：好朋友

#include <bits/stdc++.h>

using namespace std;

int Union[1010];
int Sum;

int find(int root) {
	int origin = root;
	
	while (Union[root] != root) {
		root = Union[root];
	}
	
	while (origin != root) {
		int temp = Union[origin];
		Union[origin] = root;
		origin = temp;
	}
	
	return root;
}

void join(int root1, int root2) {
	int a = find(root1);
	int b = find(root2);
	
	if (a != b) {
		Union[a] = b;
		Sum--;
	}
}

int main() {
	int N, M, f1, f2;
	
	cin >> N >> M;
	
	Sum = N;
	
	for (int i = 0; i <= N; i++) {
		Union[i] = i;
	}
	
	for (int i = 0; i < M; i++) {
		cin >> f1 >> f2;
		join(f1, f2);
	}
	
	cout << Sum;
	
	return 0;
}