poj 1251

题意：就是求最小生成树的边权值和

prim算法求最小生成树

 1 import java.util.Scanner;
 2 import java.util.Arrays;
 3 /*
 4 prim
 5 */
 6 public class Main{
 7     static int map[][];               //存储邻接矩阵
 8     static boolean visit[];           //标记加入的结点
 9     static int n;
10     static int INF = 0x3f3f3f3f;
11
12     public static int prim(){
13         int sum=0;
14         visit = new boolean[n];
15         visit[0] = true;
16
17         for(int i=0;i<n-1;i++){         //n个结点需要n-1条边，循环n-1次
18             int min = INF;
19             int u = 0;                  //保存下一个要加入树的结点下标
20             for(int j=1;j<n;j++){
21                 if(visit[j]==false&&map[0][j]<min){
22                     min = map[0][j];
23                     u = j;
24                 }
25             }
26             visit[u] = true;            //将结点加入，标记置为true
27             sum+=min;
28             for(int j=1;j<n;j++){       //更新数据
29                 if(visit[j]==false&&map[u][j]<map[0][j])
30                     map[0][j] = map[u][j];
31             }
32         }
33         return sum;
34     }
35
36     public static void main(String[] args){
37         Scanner in = new Scanner(System.in);
38         while(in.hasNext()){
39             n = in.nextInt();
40             if(n==0)
41                 break;
42             map = new int[n][n];
43             for(int i=0;i<n;i++)
44                 Arrays.fill(map[i],INF);
45             for(int i=0;i<n-1;i++){
46                 char chx = in.next().charAt(0);
47                 int j = in.nextInt();
48                 while(j!=0){
49                     j--;
50                     char chy = in.next().charAt(0);
51                     int y = chy - ‘A‘;
52                     int cost = in.nextInt();
53                     map[i][y] = map[y][i] = cost;
54                 }
55             }
56             System.out.println(prim());
57         }
58     }
59 }

Kruskal算法求最小生成树