POJ 2485 Highways Kruskal

题意：将n个小镇连接起来，求最小生成树。

题解：
#include <iostream>
using namespace std;

int t,n,father[501];

struct path
{
int u,v,w;
} edge[501 * 500 / 2];

int cmp(const void *a, const void *b)
{
return (*(path *)a).w - (*(path *)b).w;
}

int find_set ( int x )
{
if ( x != father[x] )
father[x] = find_set ( father[x] );
return father[x];
}

int Kruskal ( int x )
{
int i, ans = 0;
for ( i = 0; i < n; i++ )
father[i] = i;

qsort ( edge, x, sizeof(path), cmp );

for ( i = 0; i < x; i++ )
{
int a = find_set(edge[i].u);
int b = find_set(edge[i].v);
if ( a != b )
{
father[b] = a;
ans = edge[i].w;
}
}
return ans;
}

int main()
{
cin >> t;
while ( t-- )
{
cin >> n;
int c = 0, distance;
memset(edge,0,sizeof(edge));
for ( int i = 0; i < n; i++ )
{
for ( int j = 0; j < n; j++ )
{
cin >> distance;
if ( i < j )
{
edge[c].u = i;
edge[c].v = j;
edge[c].w = distance;
c++;
}
}
}
cout << Kruskal(c) << "\n";
}
return 0;
}