51nod 1405 树的距离之和（dfs）

 1 #pragma comment(linker, "/STACK:10240000,10240000")
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<vector>
 5 #include<algorithm>
 6 using namespace std;
 7 const int maxn = 100000+5;
 8 const int inf = 0x3f3f3f3f;
 9 
10 int n;
11 int num[maxn];
12 long long d[maxn];
13 vector<int> G[maxn];
14 
15 void dfs(int u, int fa, int dep)
16 {
17     num[u] = 1;
18     d[1] += dep;
19     for(int i=0;i<G[u].size();i++)
20     {
21         int v = G[u][i];
22         if(v==fa)  continue;
23         dfs(v,u,dep+1);
24         num[u] += num[v];
25     }
26 }
27 
28 void dfs2(int u, int fa)
29 {
30     for(int i=0;i<G[u].size();i++)
31     {
32         int v = G[u][i];
33         if(v==fa)  continue;
34         d[v] = d[u]+n-num[v]-num[v];
35         dfs2(v,u);
36     }
37 }
38 
39 int main()
40 {
41     //freopen("in.txt","r",stdin);
42     scanf("%d",&n);
43     for(int i=1;i<n;i++)
44     {
45         int u,v;
46         scanf("%d%d",&u,&v);
47         G[u].push_back(v);
48         G[v].push_back(u);
49     }
50     d[1] = 0;
51     dfs(1,0,0);
52     dfs2(1,0);
53     for(int i=1;i<=n;i++)  printf("%lld\n",d[i]);
54     return 0;
55 }