ZOJ 2966 Build The Electric System（最小生成树）

#include<string>
#include<string.h>
#include<cstring>
#include<vector>
#include<map>
#include<queue>
#include<stack>
#include<cctype>
#define mt(a) memset(a,0,sizeof a)
#define fl(a,b,c) fill(a,b,c)

#define inf 1000000000+7

using namespace std;

typedef long long ll;

int n, m;

ll graph[550][550];
int vis[550] ;
ll dis[550];

ll ans = 0;

ll prim()
{
ll i, j, pos, min, result = 0;
memset(vis, 0, sizeof vis);
fill(dis, dis + 550, inf);
vis[0] = 1; pos = 0;
dis[0] = 0;
for (i = 0; i < n; i++)
if (i != pos) dis[i] = graph[pos][i];
for (i = 0; i<n-1; i++)
{

min = inf;
for (j = 0; j < n; j++)
if (vis[j] == 0 && min>dis[j])
{
min = dis[j]; pos = j;
}
result += min;
vis[pos] = 1;
for (j = 0; j < n; j++)
if (vis[j] == 0 && dis[j]>graph[pos][j])
dis[j] = graph[pos][j];
}
return result;
}

int main()
{
int T;
cin >> T;
while (T--)
{
scanf("%d %d", &n, &m);
for (int i = 0; i <= n; i++)
{
for (int j = 0; j <= n; j++)graph[i][j] = inf;
}
memset(vis, 0, sizeof vis);

for (int i = 0; i < m; i++)
{
int x, y, k;
scanf("%d %d %lld", &x, &y, &k);
graph[x][y] = k;
graph[y][x] = k;
}
ans = prim();
printf("%lld\n", ans);
}
return 0;
}