|Tyvj|图论最小生成树|P1307 联络员

来源：互联网发布：地球空心知乎编辑：程序博客网时间：2024/05/17 01:43

http://tyvj.cn/p/1307

把必选边先全部合并，然后进行最小生成树即可，推荐用Kruskal。

下面是Kruskal代码

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;//一些定义 struct edge{int x;int y;int v;}points[10005];int father[10005];int n,m;int num = 0;int fn;//并查集基本操作 int find(int x){if (father[x]!=x)father[x] = find(father[x]);return father[x];}int merge(int x, int y){int r1 = find(x);int r2 = find(y);father[r2] = r1;}//快速排序int qs(int l, int r){int i = l, j = r, x = points[(l+r)/2].v;do{while(points[i].v<x) i++;while(points[j].v>x) j--;if (i<=j){int t = points[i].v;points[i].v = points[j].v;points[j].v = t;t = points[i].x;points[i].x = points[j].x;points[j].x = t;t = points[i].y;points[i].y = points[j].y;points[j].y = t;i++, j--;}} while(i<=j);if (l<j) qs(l,j);if (i<r) qs(i,r);}int main () { int ans = 0;scanf("%d%d", &n, &m);for (int i=1;i<=n;i++) father[i] = i;for (int i=1;i<=m;i++){int p,u,v,w;scanf("%d%d%d%d", &p, &u, &v, &w);if (p==1){if (find(u)!=find(v)) merge(u,v);ans += w;} else {num++;points[num].x = u;points[num].y = v;points[num].v = w;}}qs(1,num);int cnt = 0;for (int i=1;i<=num;i++){if (find(points[i].x)!=find(points[i].y)){merge(points[i].x, points[i].y); cnt++;ans += points[i].v;}}printf("%d\n", ans);return 0;}

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