HDU1875 畅通工程再续

题目链接。

代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

const double INF = (1<<25);

#define MAXN 103
#define MAXM 10010

struct Pos{
    int x, y;
}pos[MAXN];


int vis[MAXN];
double G[MAXN][MAXN], d[MAXN], ans;


double calc(struct Pos a, struct Pos b){
    int k = (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
    if(k<100 || k>1000000) return INF;
    else return sqrt(k*1.0);
}


int prim(int n){
    int i, x, y, flag;
    double m;


    for(i=0; i<n; i++){
        d[i] = G[0][i];
    }
    vis[0] = 1;
    d[0] = 0;


    for(i=0; i<n-1; i++){
        m = INF*1.0;
        flag = 0;
        for(y=0; y<n; y++)if(!vis[y] && m > d[y]) {m = d[x=y]; flag = 1;}
        if(!flag) break;
        vis[x] = 1;
        ans += m;
        for(y=0; y<n; y++)if(!vis[y] && d[y]>G[x][y]) d[y] = G[x][y];
    }
    return flag;
}


int main(){
    int n, i, j, T;
    scanf("%d", &T);
    while(T--){
        scanf("%d", &n);
        ans = 0.0;


        for(i=0; i<n; i++){
            scanf("%d %d", &pos[i].x, &pos[i].y);
            vis[i] = 0;
        }

        for(i=0; i<n; i++){
            for(j=0; j<=i; j++){
                if(j==i) G[i][j] = INF;
                else G[i][j] = G[j][i] = calc(pos[i], pos[j]);
            }
        }

        if(prim(n)) printf("%.1lf\n", ans*100);
        else printf("oh!\n");
    }

    return 0;
}