2560 Freckles （最小生成树）

先计算每两点的距离，然后用prime

#include<stdio.h>#include<math.h>float matr[100][100],weight[100], x[100],y[100];int main(){int n,i,j,k;float sum = 0,min = 0;scanf("%d",&n); for(i = 0;i < n;i++)scanf("%f%f",&x[i],&y[i]);for(i = 0;i < n;i++)for(j = 0;j < n;j++)matr[i][j] = 1<<30; for(i = 0;i < n-1;i++)for(j = i+1;j < n;j++)matr[i][j] = matr[j][i] = sqrt( (x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]));for(i = 0;i < n;i++)weight[i] = matr[0][i];weight[0] = 0;i = 1;while(i < n){ min = 1<<30;j = 0;while(j < n){if(weight[j]&&weight[j]<min){min = weight[j];k = j;}j++;} sum+=min;weight[k] = 0;for(j = 0;j < n;j++)if(matr[k][j] < weight[j])weight[j] = matr[k][j];i++;} printf("%.2f/n",sum);return 0;}