Agri-Net
| Time Limit: 1000MS |
|
Memory Limit: 10000K |
| Total Submissions: 25093 |
|
Accepted: 9868 |
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.
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
很顯然求這個(gè)圖的最小生成樹
然后我就打算寫prim了，寫完了之后覺(jué)得沒(méi)錯(cuò)了，但是交了好幾遍都wa了，
真心不知道錯(cuò)誤在哪里，然后去看discuss，才注意到這句話
Physically, they are limited in length to 80 characters, so some lines continue onto others.
當(dāng)時(shí)看題時(shí)候沒(méi)看明白，看別人說(shuō)的，沒(méi)行還有多余的數(shù)據(jù)
我就惡心了，我以前寫pascal還有readln可用，現(xiàn)在C語(yǔ)言有不是很熟，用什么代替呢，想了半天沒(méi)想出來(lái)
還有人說(shuō)數(shù)據(jù)范圍不止這些，不過(guò)后來(lái)驗(yàn)證后，數(shù)據(jù)范圍就是100
我就去找題解了
好多題解我發(fā)現(xiàn)都沒(méi)注意這一點(diǎn)，然后我就納悶了，有看discuss，又有人說(shuō)，不用注意這句話，我就納悶了，我找了個(gè)題解交了之后居然過(guò)了
我就在想，是不是我的prim出錯(cuò)了呢
結(jié)果一不小心瞥見(jiàn)，ans居然和vis一塊定義的，定義成short了，
呃……直接無(wú)語(yǔ)了
#include<stdio.h>
#include<string.h>
#include<math.h>
#define MAX 505
int map[MAX][MAX],cost[MAX];
short vis[MAX];
int ans;
int n;
void prim()
{
int i,j,mini,min;
memset(vis,0,sizeof(vis));
vis[1]=1;
ans=0;
for (i=1; i<=n; i++)
cost[i]=0x7fffffff;
for (i=2; i<=n; i++)
cost[i]=map[1][i];
for (i=1; i<=n-1; i++)
{
min=0x7fffffff;
for (j=1; j<=n; j++)
if ((vis[j]==0)&&(cost[j]<min))
{
min=cost[j];
mini=j;
}
vis[mini]=1;
ans=ans+min;
for (j=1; j<=n ; j++ )
if ((vis[j]==0)&&(map[mini][j]>0)&&(map[mini][j]<cost[j]))
cost[j]=map[mini][j];
}
}
void init()
{
int i,j;
memset(map,0,sizeof(map));
for (i=1; i<=n ; i++ )
{
for (j=1; j<=n ; j++ )
{
scanf("%d",&map[i][j]);
}
}
}
int main()
{
;
while (scanf("%d",&n)!=EOF)
{
init();
prim();
printf("%d\n",ans);
}
return 0;
}