畅通工程 -HDU - 1863

题意：Kruskal算法最小生成树
AC代码：
#include <iostream>
using namespace std;
const int maxn1 = 1005;
int par[maxn1];
int rank1[maxn1];

void init() {
for (int i = 0; i <= maxn1; i++) {
par[i] = i;
rank1[i] = 0;
}
}

int Find(int x) {
if (par[x] == x)
return x;
else
return par[x] = Find(par[x]);
}

void unite(int x, int y) {
x = Find(x);
y = Find(y);
if (x == y)
return;
if (rank1[x] < rank1[y])
par[x] = y;
else {
par[y] = x;
if (rank1[x] == rank1[y])
rank1[x]++;
}
}

bool same(int x, int y) {
return Find(x) == Find(y);
}

int main() {
int m, n;
while (cin >> n) {
if (n == 0)
break;
cin >> m;
init();
while (m--) {
int a[2];
scanf("%d %d", &a[0], &a[1]);
unite(a[0], a[1]);
}
int ans = 0;
for (int i = 1; i < n; ++i) {
for (int j = i + 1; j <= n; ++j) {
if (!same(i, j)) {
ans++;
unite(i,j);
}
}
}
cout<<ans<<endl;
}
return 0;
}