HDU_1232 畅通工程(并查集)
#include <iostream>
#include <cstdio>
#include <cstring>
#pragma comment(linker,"/STACK:655360000");
using namespace std;
const int N = 1002;
int f[N], rank[N];
int find(int x)
{
int k, r, j;
r = x;
while(r != f[r])
{
r = f[r];
}
k = x;
while(k != r)
{
j = f[k];
f[k] = r;
k = j;
}
return r;
}
void union_set(int a, int b)
{
int x = find(a);
int y = find(b);
if(x == y) return;
if(rank[x] > rank[y]) f[y] = x;
else
{
f[x] = y;
if(rank[x] == rank[y]) rank[y]++;
}
}
int main()
{
//freopen("data.in", "r", stdin);
int n, m, i, a, b;
while(scanf("%d", &n) != EOF)
{
if(n == 0) break;
scanf("%d", &m);
if(m == 0)
{
printf("%d\n", n-1);
continue;
}
for(i = 1;i <= n; i++)
{
f[i] = i;
rank[i] = 0;
}
while(m--)
{
cin >> a >> b;
union_set(a, b);
}
int cnt = 0;
for(i = 1; i <=n; i++)
{
if(find(i) == i) //开始写成f[i] == i了,悲剧啊!!!
cnt++;
}
printf("%d\n", cnt-1);
}
return 0;
}