loj 1357(树形dp)

题目链接：http://lightoj.com/volume_showproblem.php?problem=1357

 1 #define _CRT_SECURE_NO_WARNINGS

 2 #include <iostream>

 3 #include <cstdio>

 4 #include <cstring>

 5 #include <algorithm>

 6 #include <vector>

 7 using namespace std;

 8 

 9 const int MAXN = (100000 + 10);

10 typedef long long ll;

11 int n;

12 ll child[MAXN];

13 ll ans;

14 vector<int >g[MAXN];

15 

16 ll dfs(int u)

17 {

18     ll ret = 0;

19     for (int i = 0; i < (int)g[u].size(); i++) {

20         int v = g[u][i];

21         dfs(v);

22         ans += ret * (child[v] + 1);

23         ret += child[v] + 1;

24     }

25     return child[u] = ret;

26 }

27 

28 int main()

29 {

30     int _case, t = 1;

31     scanf("%d", &_case);

32     while (_case--) {

33         scanf("%d", &n);

34         for (int i = 1; i <= n; i++) g[i].clear();

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

36             int u, v;

37             scanf("%d %d", &u, &v);

38             g[u].push_back(v);

39         }

40         memset(child, 0, sizeof(child));

41         ans = 0;

42         dfs(1);

43         printf("Case %d: %d %lld\n", t++, n - 1, ans);

44 

45     }

46     return 0;

47 }

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