标签：算法 acm algorithm c
Tree
http://acm.hdu.edu.cn/showproblem.php?pid=2682
Time Limit: 6000/2000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1855 Accepted Submission(s): 544
Problem Description
There are N (2<=N<=600) cities,each has a value of happiness,we consider two cities A and B whose value of happiness are VA and VB,if VA is a prime number,or VB is a prime number or (VA+VB) is a prime number,then they can be connected.What‘s
more,the cost to connecte two cities is Min(Min(VA , VB),|VA-VB|).
Now we want to connecte all the cities together,and make the cost minimal.
Input
The first will contain a integer t,followed by t cases.
Each case begin with a integer N,then N integer Vi(0<=Vi<=1000000).
Output
If the all cities can be connected together,output the minimal cost,otherwise output "-1";
Sample Input
Sample Output
Author
Teddy
Source
//最小生成树 标准版
#include<cstdio>
#include<cmath>
#include<cstring>
#include<cstdlib>
#include<algorithm>
using namespace std;
const int M=1000001;
int pre[M];
int n[M];
int prime[M];
struct node
{
int start;
int end;
int value;
}num[M];
int find(int x)
{
return pre[x]==x?x:pre[x]=find(pre[x]);
}
void merge(int x,int y)
{
int fx=find(x);
int fy=find(y);
if(fx!=fy)
pre[fx]=fy;
}
int cmp(node a,node b)
{
return a.value<b.value;
}
int main()
{
memset(prime,0,sizeof(prime));
__int64 i,j;
prime[0]=prime[1]=1;
for(i=2;i<1001;i++)
if(!prime[i])
for(j=i*i;j<M;j+=i)
prime[j]=1;
int t;
scanf("%d",&t);
while(t--)
{
int city,k;
scanf("%d",&city);
for(i=1;i<=city;i++)
{
scanf("%d",&n[i]);
pre[i]=i;
}
k=0;
memset(num,0,sizeof(num));
for(i=1;i<=city;i++)
for(j=i+1;j<=city;j++)
if(!prime[n[i]]||!prime[n[j]]||!prime[n[i]+n[j]])
{
num[k].start=i;
num[k].end=j;
num[k].value=min(min(n[i],n[j]),abs(n[i]-n[j]));
k++;
}
sort(num,num+k,cmp);
__int64 ans=0;
for(i=0;i<k;i++)
{
int fx=find(num[i].start);
int fy=find(num[i].end);
if(fx!=fy)
{
merge(fx,fy);
ans+= num[i].value;
}
}
int count=0;
for(i=1;i<=city;i++)
{
if(pre[i]==i)
count++;
if(count>1)
break;
}
if(count>1)
printf("-1\n");
else
printf("%I64d\n",ans);
}
return 0;
} hdoj 2682 Tree(最小生成树)
标签：算法 acm algorithm c
原文地址：http://blog.csdn.net/lh__huahuan/article/details/44904979
