[2016-04-14] [POJ] [1258] [Agri-net]

• Time: 2016-04-14-20:36:55 Thursday
• Title number: [2016-04-14][poj][1258][agri-net]
• The main idea: to find the minimum spanning tree
• Analysis: Direct PRIM algorithm

  
 

   
  

  
#include<cstdio>
   
  

  
#include<cstring>
   
  

  
#include<algorithm>
   
  

  
using namespace std;
   
  

  
const int maxn = 100 + 10 ;
   
  

  
int g[maxn][maxn],vis[maxn],lowc[maxn];
   
  

  
int prim(int n){
   
  

  
 int ans = 0;
   
  

  
 memset(vis,0,sizeof(vis));
   
  

  
 Vis  [ 0  ]    =    1  ;   
   
  

  
  for   ( int   i  =    1    ;   I  <   n     ++  i  )   LOWC  [ i  ]    =   g  [ 0  ][ i  ;   
   
  

  
 for(int i = 1 ; i < n ;++i){
   
  

  
 int minc = 0x3f3f3f3f;
   
  

  
 int p = -1;
   
  

  
 for(int j = 0 ; j < n ; ++j){
   
  

  
 if(!vis[j] && minc > lowc[j]){
   
  

  
 minc = lowc[j];
   
  

  
 p = j;
   
  

  
 }
   
  

  
 }
   
  

  
 if(minc == 0x3f3f3f3f) return -1;
   
  

  
 ans += minc;
   
  

  
 vis[p] = 1;
   
  

  
 for(int j = 0 ; j < n ; ++j){
   
  

  
  if   (! vis  [ j  ]    &&   LOWC  [  j  ]    >   g  [ p  ][  j  ]) {  
   
  

  
 lowc[j] = g[p][j];
   
  

  
 }
   
  

  
 }
   
  

  
 }
   
  

  
 return ans;
   
  

  
}
   
  

  
int main(){
   
  

  
 int n,a;
   
  

  
 while(~scanf("%d",&n)){
   
  

  
 memset(g,0x3f,sizeof(g));
   
  

  
 for(int i = 0 ; i < n ; ++i){
   
  

  
 for(int j = 0 ; j < n ; ++j){
   
  

  
 scanf("%d",&a);
   
  

  
 g[i][j] = min(g[i][j],a);
   
  

  
 } 
   
  

  
 }
   
  

  
 printf("%d\n",prim(n));
   
  

  
 }
   
  

  
 return 0;
   
  

  
}
  
 

From for notes (Wiz)

[2016-04-14] [POJ] [1258] [Agri-net]