poj2485

最小生成树

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

#define maxn 505
#define inf 0x3f3f3f3f

int n, cost[maxn][maxn];
bool vis[maxn];
int lowcost[maxn];

void input()
{
    scanf("%d", &n);
    for (int i = 0; i < n; i++)
        for (int j = 0; j < n; j++)
            scanf("%d", &cost[i][j]);
}

int prim()
{
    int ret = 0, pre, best;

    memset(vis, 0, sizeof(vis));
    for (int i = 0; i < n; i++)
        lowcost[i] = inf;
    lowcost[0] = 0;
    vis[0] = true;
    pre = 0;
    while (1)
    {
        for (int i = 0; i < n; i++)
            if (!vis[i] && lowcost[i] > cost[pre][i])
                lowcost[i] = cost[pre][i];
        best = inf;
        pre = -1;
        for (int i = 0; i < n; i++)
            if (!vis[i] && lowcost[i] < best)
            {
                pre = i;
                best = lowcost[i];
            }
        if (pre == -1)
            break;
        vis[pre] = true;
        ret = max(ret, lowcost[pre]);
        lowcost[pre] = 0;
    }
    return ret;
}

int main()
{
    //freopen("t.txt", "r", stdin);
    int t;
    scanf("%d", &t);
    while (t--)
    {
        input();
        printf("%d\n", prim());
    }
    return 0;
}