[51NOD1405] 树的距离之和（树DP）

 1 #include <bits/stdc++.h>
 2 #include<ext/pb_ds/assoc_container.hpp>
 3 #pragma comment(linker, "/STACK:10240000,10240000")
 4 using namespace std;
 5 using namespace __gnu_pbds;
 6 
 7 typedef long long LL;
 8 const int maxn = 200100;
 9 vector<int> G[maxn];
10 LL num[maxn];
11 LL dp[maxn];
12 int n;
13 
14 LL dfs1(int u, int p, LL d) {
15   int cnt = 1;
16   num[u] = cnt;
17   dp[1] += d;
18   for(int i = 0; i < G[u].size(); i++) {
19     int v = G[u][i];
20     if(v == p) continue;
21     num[u] += dfs1(v, u, d+1);
22   }
23   return num[u];
24 }
25 
26 void dfs2(int u, int p) {
27   for(int i = 0; i < G[u].size(); i++) {
28     int v = G[u][i];
29     if(v == p) continue;
30     dp[v] = dp[u] + n - num[v] * 2;
31     dfs2(v, u);
32   }
33 }
34 
35 int main() {
36   //freopen("in", "r", stdin);
37   int u, v;
38   while(~scanf("%d", &n)) {
39     memset(num, 0, sizeof(num));
40     memset(dp, 0, sizeof(dp));
41     for(int i = 1; i <= n; i++) G[i].clear();
42     for(int i = 1; i < n; i++) {
43       scanf("%d%d",&u,&v);
44       G[u].push_back(v);
45       G[v].push_back(u);
46     }
47     dfs1(1, -1, 0);
48     dfs2(1, -1);
49     for(int i = 1; i <= n; i++) printf("%lld\n", dp[i]);
50   }
51   return 0;
52 }