pku1655 Balancing Act

http://poj.org/problem?id=1655
树状DP，双向建图，以1为树的根节点遍历一遍
 1 #include <stdio.h>
 2 #include <string.h>
 3 #include <vector>
 4 
 5 #define N 20010
 6 
 7 using namespace std;
 8 
 9 vector<int> a[N];
10 
11 int n, mark[N], result, resulti;
12 
13 int dfs(int x)
14 {
15     int i, j, temp, sum = 1, max_son = 0;
16     //printf("%d: ( ", x);
17     for(i=0; i<a[x].size(); i++)
18     {
19         j = a[x][i];
20         if(!mark[j])
21         {
22             mark[j] = 1;
23             temp = dfs(j);
24             sum += temp;
25             max_son = max(max_son, temp);
26         }
27     }
28     max_son = max(n-sum, max_son);
29     if(max_son < result)
30     {
31         result = max_son;
32         resulti = x;
33     }
34     //printf(" *%d %d) ", sum, max_son);
35     return sum;
36 }
37 
38 int main()
39 {
40     int t, i, x, y;
41     scanf("%d", &t);
42     while(t-- && scanf("%d", &n))
43     {
44         for(i=1; i<=n; i++)
45         {
46             a[i].clear();
47         }
48         for(i=2; i<=n; i++)
49         {
50             scanf("%d%d", &x, &y);
51             a[x].push_back(y);
52             a[y].push_back(x);
53         }
54         memset(mark, 0, sizeof(mark));
55         result = 1<<30;
56         resulti = -1;
57         mark[1] = 1;
58         dfs(1);
59         printf("%d %d\n", resulti, result);
60     }
61     return 0;
62 }