POJ 1258（最小生成树+知识）

#include <cstdio>
#include <iostream>
#include <queue>
using namespace std;

#define sf scanf
#define pf printf
#define debug printf("!\n")
#define blank printf("\n")
#define mem(a,b) memset(a,b,sizeof(a))

const int MaxN = 110;
const int INF = 1<<27;

int p[MaxN];

int map[MaxN][MaxN],w[MaxN*MaxN],r[MaxN*MaxN],u[MaxN*MaxN],v[MaxN*MaxN];

int m,n;

int find(int x){return p[x]==x?x:p[x]=find(p[x]);}


int cmp(const int a,const int b)
{
    return w[a]<w[b];
}

int kruskal()
{
    int ans = 0,i;

    for(i = 0;i<n;i++) p[i] = i;
    for(i = 0;i<m;i++) r[i] = i;
    
    sort(r,r+m,cmp);

    for(i = 0;i<m;i++)
    {
        int e = r[i];
        int x = find(u[e]);
        int y = find(v[e]);
        if(x!=y)
        {
            ans+=w[e];p[x] = y;
        }
    }
    return ans;
}


int main()
{
    int i,j;
    while(~sf("%d",&n))
    {
        m = 0;
        mem(u,0);
        mem(v,0);
        mem(w,0);
        for(i = 0;i<n;i++)
        {
            for(j=0;j<n;j++)
                sf("%d",&map[i][j]);
        }
        for(i = 0;i<n;i++)
        {
            for(j=i+1;j<n;j++)
            {
                u[m] = i;
                v[m] = j;
                w[m++] = map[i][j];
            }
        }
        int ans = kruskal();
        pf("%d\n",ans);

    }

    return 0;
}