HDU - 1232 畅通工程（简单并查集）

Description

Input

Output

Sample Input

4 2
1 3
4 3
3 3
1 2
1 3
2 3
5 2
1 2
3 5
999 0
0 

Sample Output

1
0
2
998 

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;

const int MAXN = 1010;
int parent[MAXN];
int n, m;

void make_set()
{
	for (int i = 0; i <= n; i++)
		parent[i] = -1;
}

int find_set(int t)
{
	if (parent[t] == -1)
		return t;
	else
		return parent[t]=find_set(parent[t]);
}

void union_set(int a, int b)
{
	int t1 = find_set(a);
	int t2 = find_set(b);
	if (t1 != t2)
		parent[t2] = t1;
}

int main()
{
	int a, b;
	while (scanf("%d", &n) != EOF&&n)
	{
		scanf("%d", &m);
		make_set();
		for (int i = 0; i < m; i++)
		{
			scanf("%d%d", &a, &b);
			union_set(a, b);
		}
		int sum = 0;
		for (int i = 1; i <= n;i++)
		if (parent[i] == -1)
			sum++;
		printf("%d\n", sum-1);
	}
}