HDU3371 Connect the Cities 解题报告--prim

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Connect the Cities

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 6549    Accepted Submission(s): 1884


Problem Description
In 2100, since the sea level rise, most of the cities disappear. Though some survived cities are still connected with others, but most of them become disconnected. The government wants to build some roads to connect all of these cities again, but they don’t want to take too much money.  
 

Input
The first line contains the number of test cases.
Each test case starts with three integers: n, m and k. n (3 <= n <=500) stands for the number of survived cities, m (0 <= m <= 25000) stands for the number of roads you can choose to connect the cities and k (0 <= k <= 100) stands for the number of still connected cities.
To make it easy, the cities are signed from 1 to n.
Then follow m lines, each contains three integers p, q and c (0 <= c <= 1000), means it takes c to connect p and q.
Then follow k lines, each line starts with an integer t (2 <= t <= n) stands for the number of this connected cities. Then t integers follow stands for the id of these cities.
 

Output
For each case, output the least money you need to take, if it’s impossible, just output -1.
 

Sample Input
16 4 31 4 22 6 12 3 53 4 332 1 22 1 33 4 5 6
 

Sample Output
1
 

Author
dandelion
 

Source
HDOJ Monthly Contest – 2010.04.04
 

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#include<iostream>#define inf 0xffffusing namespace std;int map[700][700];int n,m;int flag;int prim(){int sum=0;int lowcost[1001];int mark[1001];memset(mark,0,sizeof(mark));for(int i=0;i<n;i++){lowcost[i]=map[0][i];}mark[0]=1;int pos;for(i=1;i<n;i++){int Min=inf;for(int j=0;j<n;j++){if(Min>lowcost[j]&&mark[j]==0){Min=lowcost[j];pos=j;}}if(Min==inf) {return -1;break;}mark[pos]=1;sum+=Min;for(j=0;j<n;j++){if(lowcost[j]>map[pos][j]&&mark[j]==0){lowcost[j]=map[pos][j];}}}return sum;}int main(){int k;int r;scanf("%d",&r);while(r--){scanf("%d%d%d",&n,&m,&k);for(int i=0;i<n;i++){for(int j=0;j<n;j++){map[i][j]=inf;}}for(i=0;i<m;i++){int a,b,c;scanf("%d%d%d",&a,&b,&c);if(c<map[b-1][a-1])map[b-1][a-1]=map[a-1][b-1]=c;}int j;for(i=0;i<k;i++){int kk;int orz[1001];scanf("%d",&kk);for(j=0;j<kk;j++)scanf("%d",&orz[j]);for(j=0;j<kk;j++)for(int p=0;p<kk;p++)map[orz[j]-1][orz[p]-1]=0;}printf("%d\n",prim());}return 0;}

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