HDU 1162 Eddy's picture

最小生成树..

#include <iostream>
#include <string.h>
#include <math.h>
#include <iomanip>
using namespace std;
const int MAXN = 101;

struct point {
    double x,y;
};
point p[MAXN];
double G[MAXN][MAXN];
double lowcost[MAXN];
int closest[MAXN];
bool used[MAXN];
double cost;

void PRIM(int n){
    cost = 0;
    used[1] = true;
    for(int i = 2; i <= n; i++){
        lowcost[i] = G[1][i];
        closest[i] = 1;
        used[i] = false;
    }
    double min;
    int minIndex;
    for(int i = 1; i < n; i++){
        min = 32767.0;
        for(int j = 1; j <= n; j++){
            if( !used[j] && min > lowcost[j] ){
                min = lowcost[j];
                minIndex = j;
            }
        }
        used[minIndex] = true;
        cost += min;
        for(int j = 1; j <= n;j++){
            if( !used[j] && G[minIndex][j] < lowcost[j])
                lowcost[j] = G[minIndex][j];
        }
    }
}

int main(){
    int N;
    double x,y,dis;
    while(scanf("%d",&N) == 1){
        for(int i = 1; i <= N; i++){
            scanf("%lf%lf",&p[i].x,&p[i].y); 
        }
        memset(G,0,sizeof(G));
        for(int i = 1; i <= N; i++)
            for(int j = 1; j <= N; j++)
                G[i][j] = sqrt((p[i].x-p[j].x)*(p[i].x-p[j].x)+(p[i].y-p[j].y)*(p[i].y-p[j].y));
        PRIM(N);
        printf("%.2f\n",cost);
    }
    return 0;
}