prim最小生成树算法题poj2485

#include<cstdio>
#include<queue>
#include<set>
using namespace std;
int a[2510][25100];
struct weight
{
    int a,b;
    int value;
    bool operator < (const weight & rhs) const
    {
        return value < rhs.value;
    }
     bool operator > (const weight & rhs) const
    {
        return value > rhs.value;
    }
};
int sett[251000];

int find2(int x)
{
    while(x != sett[x]) x=sett[x];
    return x;
}
void merge2(int a,int b)
{
    if(a > b) sett[a]=b;
    else sett[b]=a;
}
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        priority_queue<weight , vector<weight> , greater<weight> > pq;
        int n;
        scanf("%d",&n);
        for(int i=0;i<n;i++) sett[i]=i;
        for(int i=0;i<n;i++)
            for(int j=0;j<n;j++){
                int x;
                scanf("%d",&x);
                if(x == 0) x = 65537;
                weight route;
                route.a=i;
                route.b=j;
                route.value=x;
                pq.push(route);
            }

        set<int> drop;

//        printf("size=%d n=%d\n",drop.size(),n);
        while(drop.size() != n-1){
//            printf("size=%d n=%d\n",drop.size(),n);
            weight mi = pq.top();
            pq.pop();
            int fx =find2(mi.a);
            int fy =find2(mi.b);

            if(fx!=fy){
                drop.insert(mi.value);
                merge2(fx,fy);
            }

        }
//        printf("size%d\n",drop.size() );
//        for(set<int>::iterator it=drop.begin();it!=drop.end();it++){
//            printf("dsa\n");
//            printf("%d ",*it);
//        }
        set<int>::iterator it = drop.end();
        it--;
        printf("%d\n",*it );

    }
    return 0;
}
/*
1
4
0 1 2 3
1 0 2 3
2 2 0 3
3 3 3 0

-1073741819
-1073741819
*/

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int cost[510][510];
int mincost[510];
bool used[510];
int n;
int prim()
{
    memset(used,false,sizeof(used));
    memset(mincost,65537,sizeof(mincost));
    int MAXres=0;
    mincost[0]=0;
    while(true){
        int v=-1;
        for(int i=0;i<n;i++)
            if(!used[i] && ( v==-1 || mincost[i]<mincost[v])  ) v=i;
        if(v == -1) break;
        used[v]=true;

        if(mincost[v] >MAXres)MAXres=mincost[v];
        for(int i=0;i<n;i++)
            mincost[i] = min(mincost[i], cost[v][i]);
    }
    return MAXres;
}
int main()
{
    int cases;
    scanf("%d",&cases);
    while(cases--){

            scanf("%d",&n);
    for(int i=0;i<n;i++)
        for(int j=0;j<n;j++)
    {
        int x;
        scanf("%d",&cost[i][j]);
        if(cost[i][j]== 0) cost[i][j] = 65537;
    }
    printf("%d\n",prim());

    }

    return 0;
}