POJ 2524 Ubiquitous Religions (并查集)

#include <stdio.h>
#define MAX_STDDENTS 50000
int numOfStudents, numOfPairs;
int religion[MAX_STDDENTS + 1];
int rank[MAX_STDDENTS + 1];

void makeSet(){
	int student;
		for (student = 1; student <= numOfStudents; student++){
			religion[student] = student;
			rank[student] = 0;
		}
}

int findSet(int student){
	if (student != religion[student])
		//路径压缩
		religion[student] = findSet(religion[student]);
	return religion[student];
}

void unionSet(int one, int another){
	//按秩合并
	if (rank[one] > rank[another]){
		religion[another] = religion[one];
	} else {
		religion[one] = religion[another];
		//更新秩，秩为集合树的高
		if (rank[one] == rank[another])
			rank[another]++;
	}
}

int main(){

	int testcase = 1;
	while (1){
		scanf("%d%d", &numOfStudents, &numOfPairs);
		if (numOfStudents == 0 && numOfPairs == 0)
			return 0;

		makeSet();
		
		int result = numOfStudents;
		int pair;
		for (pair = 1; pair <= numOfPairs; pair++){
			int one, another;
			scanf("%d%d", &one, &another);
			one = findSet(one);
			another = findSet(another);
			if (one != another){
				result--;
				unionSet(one, another);
			}
		}

		printf("Case %d: %d\n", testcase++, result);

	}	
}