poj - 3107 Godfather

和poj 1655类似，也是拆了一个树求什么值。这题我改进了一下，把两个DFS合一了。

 1 #include <stdio.h>
 2 #define N 50005
 3 int fst[N],nxt[N<<1],to[N<<1];
 4 int n,s[N],w[N],min;
 5 int dfs(int u,int fa)
 6 {
 7     int i,v,t=n-1;
 8     s[u] = 1; w[u] = 0;
 9     for(i = fst[u]; i != 0; i = nxt[i])
10     {
11         v = to[i];
12         if(v != fa)
13             s[u] += dfs(v,u);
14     }
15     //printf("s[%d]:%d\n",u,s[u]);
16     for(i = fst[u]; i != 0; i = nxt[i])
17     {
18         v = to[i];
19         if(v != fa)
20         {
21             t -= s[v];
22             if(s[v] > w[u]) w[u]=s[v];
23         }
24     }
25     if(t > w[u]) w[u]=t;
26     //printf("w[%d]:%d\n",u,w[u]);
27     if(w[u] < min) min = w[u];
28     return s[u];
29 }
30 int main()
31 {
32     int a,b,i,j,f=1;
33     scanf("%d",&n);
34     min = n;
35     for(i = j = 1; j < n; j++)
36     {
37         scanf("%d%d",&a,&b);
38         to[i] = b;
39         nxt[i] = fst[a];
40         fst[a] = i++;
41         to[i] = a;
42         nxt[i] = fst[b];
43         fst[b] = i++;
44     }
45     dfs(1,0);
46     for(i = 1; i <= n; i++)if(w[i] == min)
47     {
48         if(f) printf("%d",i), f = 0;
49         else printf(" %d",i);
50     }
51     printf("\n");
52     return 0;
53 }

转载于:https://www.cnblogs.com/lzxskjo/archive/2012/11/08/2761671.html