uva10397

题目链接请戳 这里

 

解题思路

数据好像加强了，，，Kruskal过不了（还是我写搓了？）。。。

用Prim吧。把已经存在的边，距离都设为0（反向边也是），这样生成的MST一定

会包含这些边。

 

代码

#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
#define N 1010
#define INF 1e9+5
using namespace std;

struct building {
    int x, y;
}buid[N];
double w[N][N];
int vis[N];
double d[N];
int n;

double path(building a, building b)
{
    return sqrt(pow(a.x - b.x, 2) + pow(a.y - b.y, 2));
}

double Prim()
{
    memset(vis, 0, sizeof(vis));
    double ans = 0;
    for(int i = 1; i <= n; i++) d[i] = (i == 1 ? 0 : INF);
    for(int i = 1; i <= n; i++) {
        int x; double m = INF;
        for(int y = 1; y <= n; y++) if(!vis[y] && d[y] < m) m = d[x = y];
        vis[x] = 1; ans += m;
        for(int y = 1; y <= n; y++) if(!vis[y]) d[y] = min(d[y], w[x][y]);
    }
    return ans;
}

int main()
{
    while(scanf("%d", &n) != EOF) {
        for(int i = 1; i <= n; i++) {
            scanf("%d%d", &buid[i].x, &buid[i].y);
        }
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++) 
                if(i != j)
                    w[j][i] = w[i][j] = path(buid[i], buid[j]);
                else w[i][j] = INF;
        int t;
        scanf("%d", &t);
        for(int i = 0; i < t; i++) {
            int a, b;
            scanf("%d%d", &a, &b);
            w[a][b] = w[b][a] = 0;
        }
        double ans = Prim();
        printf("%.2lf\n", ans);
    }
    return 0;
}