HDOJ 1102 Constructing Roads(最小生成树)

Constructing Roads

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 17206    Accepted Submission(s): 6532

Problem Description

There are N villages, which are numbered from 1 to N, and you should build some roads such that every two villages can connect to each other. We say two village A and B are connected, if and only if there is a road between A and B, or there exists a village C such that there is a road between A and C, and C and B are connected.

We know that there are already some roads between some villages and your job is the build some roads such that all the villages are connect and the length of all the roads built is minimum.

 

Input

The first line is an integer N (3 <= N <= 100), which is the number of villages. Then come N lines, the i-th of which contains N integers, and the j-th of these N integers is the distance (the distance should be an integer within [1, 1000]) between village i and village j.

Then there is an integer Q (0 <= Q <= N * (N + 1) / 2). Then come Q lines, each line contains two integers a and b (1 <= a < b <= N), which means the road between village a and village b has been built.

 

Output

You should output a line contains an integer, which is the length of all the roads to be built such that all the villages are connected, and this value is minimum.

 

Sample Input

30 990 692990 0 179692 179 011 2

 

Sample Output

179

 

 

 

坑啊，这特么的输出样例真不懂，QAQ。。。英语瞎子

 

题意：有n个城市，给出一个n*n矩阵，矩阵中第i行第j个数表示城市i与j间的距离。再给出Q，有Q行数据表示x城市与y城市间已经有道路，求出，畅通所有城市需要建设的道路的最小长度。

 

Kruskal算法，将矩阵化为结构体储存好城市间信息即可，代码如下：

 

#include<cstdio>#include<algorithm>using namespace std;int set[110];struct node{int s,e,w;}row[10010];int cmp(node a,node b){return a.w<b.w;}int find(int x){int r=x,t;while(r!=set[r])   r=set[r];while(x!=r){t=set[x];set[x]=r;        x=t;}return r;} int merge(int a,int b){int fa,fb;fa=find(a);fb=find(b);if(fa!=fb)    {    set[fa]=fb;    return 1;    }    return 0;}int main(){int n,i,j,k,way,Q,x,y,sum;while(scanf("%d",&n)!=EOF){for(i=1;i<=n;i++)   set[i]=i;k=0;for(i=1;i<=n;i++){for(j=1;j<=n;j++){scanf("%d",&way);if(j>i){row[k].s=i;    row[k].e=j;    row[k].w=way;    k++;}}}sort(row,row+k,cmp);scanf("%d",&Q);for(i=0;i<Q;i++){scanf("%d%d",&x,&y);merge(x,y);//注意合并根节点啊，wa了好几次 }sum=0;for(i=0;i<k;i++){if(merge(row[i].s,row[i].e))  sum+=row[i].w;}printf("%d\n",sum);}return 0;}