HDU 2196 Computer（树的直径）

题目:给你一棵树，求任何正确的最长距离

思路:首先选择一个点，一次求DFS，找出树上直径的一个端点，然后用这个端点再次找出另一个树的直径端点，然后从这个端点起点求DFS，每次更新D数组。

原理：从树上的任何节点到树上任何节点的最远端点必须是树上直径的两个端点之一

#include <cstdio>#include <queue>#include <cstring>#include <iostream>#include <cstdlib>#include <algorithm>#include <vector>#include <map>#include <string>#include <set>#include <ctime>#include <cmath>#include <cctype>using namespace std;#define maxn 10010#define LL long longint cas=1,T;struct Edge{int v,w;Edge(int vv,int ww):v(vv),w(ww){}};int d[maxn];int maxlen;vector<vector<Edge> >e;int End=0;void dfs(int u,int fa,int len){if (len>maxlen)maxlen=len,End=u;for (int i = 0;i<e[u].size();i++){int v = e[u][i].v,w=e[u][i].w;if (v==fa)continue;dfs(v,u,len+w);d[v]=max(d[v],len+w);}}int main(){int n;while (scanf("%d",&n)!=EOF){    e.clear();e.resize(n+2);        for (int i = 2;i<=n;i++){int v,w;scanf("%d%d",&v,&w);e[i].push_back(Edge(v,w));e[v].push_back(Edge(i,w));}memset(d,0,sizeof(d));maxlen=0;dfs(1,-1,0);dfs(End,-1,0);dfs(End,-1,0);for (int i = 1;i<=n;i++)printf("%d\n",d[i]);}//freopen("in","r",stdin);//scanf("%d",&T);//printf("time=%.3lf",(double)clock()/CLOCKS_PER_SEC);return 0;}

Description

A school bought the first computer some time ago(so this computer's id is 1). During the recent years the school bought N-1 new computers. Each new computer was connected to one of settled earlier. Managers of school are anxious about slow functioning of the net and want to know the maximum distance Si for which i-th computer needs to send signal (i.e. length of cable to the most distant computer). You need to provide this information.

Hint: the example input is corresponding to this graph. And from the graph, you can see that the computer 4 is farthest one from 1, so S1 = 3. Computer 4 and 5 are the farthest ones from 2, so S2 = 2. Computer 5 is the farthest one from 3, so S3 = 3. we also get S4 = 4, S5 = 4.

Input

Input file contains multiple test cases.In each case there is natural number N (N<=10000) in the first line, followed by (N-1) lines with descriptions of computers. i-th line contains two natural numbers - number of computer, to which i-th computer is connected and length of cable used for connection. Total length of cable does not exceed 10^9. Numbers in lines of input are separated by a space.

Output

For each case output N lines. i-th line must contain number Si for i-th computer (1<=i<=N).

Sample Input

51 12 13 11 1

Sample Output

32344