UVA 10397 - Connect the Campus

来源：互联网发布：洗车哪个软件好编辑：程序博客网时间：2024/06/05 09:24

最小生成树问题，注意消去固定边时的方法：

#include<stdio.h>#include<string.h>#include<stdlib.h>#include<math.h>#define MAXN 800#define MAXN1 300000double x[MAXN], y[MAXN], w[MAXN1];int n, p1, m, p[MAXN], u[MAXN1], v[MAXN1], r[MAXN1], vis[1010][1010];int cmp(const void *_i, const void *_j){    int *i = (int *)_i;    int *j = (int *)_j;    return w[*i] > w[*j] ? 1 : -1;}int find(int x) {return p[x] == x ? x : p[x] = find(p[x]);}double kruskal(){    double ans = 0;    for(int i = 0; i <= n; i ++) p[i] = i;    for(int i = 0; i < p1; i ++) r[i] = i;    qsort(r,p1,sizeof(r[0]),cmp);    for(int i = 0; i < p1; i ++)    {        int e = r[i]; int x1 = find(u[e]); int y1 = find(v[e]);        if(x1 != y1){ans += w[e]; p[x1] = y1;}    }    return ans;}void init(){    while(~scanf("%d",&n))    {        memset(vis,0,sizeof(vis));        for(int i = 1; i <= n; i ++)            scanf("%lf%lf",&x[i], &y[i]);        scanf("%d",&m);        for(int i = 0; i < m; i ++)        {            int z, c;            scanf("%d%d",&z, &c);            if(z > c) vis[c][z] = 1;            else vis[z][c] = 1;        }        p1 = 0;        for(int i = 1; i <= n; i ++)        {            for(int j = i+1; j <= n; j ++)            {                if(vis[i][j]) w[p1] = 0;                else                        w[p1] = sqrt((x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]));                u[p1] = i;                v[p1] = j;                p1 ++;            }        }        printf("%.2f\n",kruskal());    }}int main(){    init();    return 0;}

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