http://acm.hdu.edu.cn/showproblem.php?pid=1162
最小生成树
1 #include<iostream> 2 #include<stdio.h> 3 #include<math.h> 4 #include<string.h> 5 #include<stdlib.h> 6 using namespace std; 7 const int N=5005; 8 struct stu{ 9 int u; 10 int v; 11 double w; 12 }p[N]; 13 14 struct ln{ 15 double x; 16 double y; 17 }q[N]; 18 int father[N]; 19 int n,m,k; 20 21 int cmp(const void *a,const void *b) 22 { 23 return (*(struct stu*)a).w > (*(struct stu*)b).w ?1:-1; 24 } 25 int find(int x) 26 { 27 if(father[x]!=x) 28 father[x]=find(father[x]); 29 return father[x]; 30 } 31 int make(int a,int b) 32 { 33 int h=0; 34 int f1=find(a); 35 int f2=find(b); 36 if(f1>f2) 37 { 38 father[f1]=f2; 39 h=1; 40 } 41 else if(f1<f2) 42 { 43 father[f2]=f1; 44 h=1; 45 } 46 return h; 47 } 48 double kruskal() 49 { 50 int cnt=0; 51 double s=0; 52 for(int i=0;i<k;i++) 53 { 54 if(make(p[i].u,p[i].v)) 55 { 56 s+=p[i].w; 57 cnt++; 58 } 59 if(cnt==n-1) 60 return s; 61 } 62 return s; 63 } 64 void zuhe() 65 { 66 k=0; 67 for(int i=0;i<n;i++) 68 { 69 for(int j=i+1;j<n;j++) 70 { 71 p[k].u=i+1; 72 p[k].v=j+1; 73 p[k++].w=sqrt((q[i].x-q[j].x)*(q[i].x-q[j].x)+(q[i].y-q[j].y)*(q[i].y-q[j].y)); 74 } 75 } 76 } 77 78 int main() 79 { 80 //freopen("in.txt","r",stdin); 81 while(~scanf("%d",&n)) 82 { 83 for(int i=1;i<=n;i++) 84 father[i]=i; 85 for(int i=0;i<n;i++) 86 { 87 scanf("%lf%lf",&q[i].x,&q[i].y); 88 } 89 zuhe(); 90 qsort(p,k,sizeof(struct stu),cmp); 91 // for(int i=0;i<k;i++) 92 // { 93 // printf("%d %d %lf ",p[i].u,p[i].v,p[i].w); 94 // } 95 printf("%.2lf ",kruskal()); 96 } 97 return 0; 98 }