Agri-Net
| Time Limit: 1000MS | Memory Limit: 10000K | |
| Total Submissions: 38406 | Accepted: 15469 |
Description
Farmer John has been elected mayor of his town! One of his campaign promises was to bring internet connectivity to all farms in the area. He needs your help, of course.
Farmer John ordered a high speed connection for his farm and is going to share his connectivity with the other farmers. To minimize cost, he wants to lay the minimum amount of optical fiber to connect his farm to all the other farms.
Given a list of how much fiber it takes to connect each pair of farms, you must find the minimum amount of fiber needed to connect them all together. Each farm must connect to some other farm such that a packet can flow from any one farm to any other farm.
The distance between any two farms will not exceed 100,000.
Farmer John ordered a high speed connection for his farm and is going to share his connectivity with the other farmers. To minimize cost, he wants to lay the minimum amount of optical fiber to connect his farm to all the other farms.
Given a list of how much fiber it takes to connect each pair of farms, you must find the minimum amount of fiber needed to connect them all together. Each farm must connect to some other farm such that a packet can flow from any one farm to any other farm.
The distance between any two farms will not exceed 100,000.
Input
The
input includes several cases. For each case, the first line contains the
number of farms, N (3 <= N <= 100). The following lines contain
the N x N conectivity matrix, where each element shows the distance from
on farm to another. Logically, they are N lines of N space-separated
integers. Physically, they are limited in length to 80 characters, so
some lines continue onto others. Of course, the diagonal will be 0,
since the distance from farm i to itself is not interesting for this
problem.
Output
For
each case, output a single integer length that is the sum of the
minimum length of fiber required to connect the entire set of farms.
Sample Input
4 0 4 9 21 4 0 8 17 9 8 0 16 21 17 16 0
Sample Output
28
水题一道。最小生成树。prim即可
1 /*====================================================================== 2 * Author : kevin 3 * Filename : AgriNet.cpp 4 * Creat time : 2014-07-09 15:55 5 * Description : 6 ========================================================================*/ 7 #include <iostream> 8 #include <algorithm> 9 #include <cstdio> 10 #include <cstring> 11 #include <queue> 12 #include <cmath> 13 #define clr(a,b) memset(a,b,sizeof(a)) 14 #define M 200 15 #define INF 0x7f7f7f7f 16 using namespace std; 17 int c[M][M],dis[M]; 18 int prim(int n) 19 { 20 bool vis[M]; 21 int i,j,k,sum = 0; 22 for(i = 0; i < n; i++){ 23 dis[i] = c[0][i]; 24 vis[i] = false; 25 } 26 vis[0] = true; 27 for(i = 1; i < n; i++){ 28 int _min = INF; 29 j = 0; 30 for(k = 0; k < n; k++){ 31 if(_min > dis[k] && !vis[k]){ 32 _min = dis[k]; 33 j = k; 34 } 35 } 36 vis[j] = true; 37 sum += dis[j]; 38 for(k = 0; k < n; k++){ 39 if(dis[k] > c[j][k] && !vis[k]){ 40 dis[k] = c[j][k]; 41 } 42 } 43 } 44 return sum; 45 } 46 int main() 47 { 48 int n; 49 while(scanf("%d",&n)!=EOF){ 50 clr(c,0); 51 int value; 52 for(int i = 0; i < n; i++){ 53 for(int j = 0; j <n; j++){ 54 scanf("%d",&value); 55 c[i][j] = value; 56 } 57 } 58 int ans = prim(n); 59 printf("%d\n",ans); 60 } 61 }