hdu--2196--树上某点到其余结点的最远距离

 1 #include <iostream>
 2 #include <cstring>
 3 #include <queue>
 4 #include <algorithm>
 5 using namespace std;
 6 
 7 int cnt;
 8 const int size = 10010;
 9 struct data
10 {
11     int to;
12     int val;
13     int next;
14 }node[size*2];
15 int head[size];
16 int dist1[size];
17 int dist2[size];
18 bool vis[size];
19 
20 void init( )
21 {
22     memset( head , -1 , sizeof(head) );
23     memset( dist1 , 0 , sizeof(dist1) );
24     memset( dist2 , 0 , sizeof(dist2) );
25 }
26 
27 void addEdge( int from , int to , int dist )
28 {
29     node[cnt].to = to;
30     node[cnt].val = dist;
31     node[cnt].next = head[from];
32     head[from] = cnt ++;
33 }
34 
35 int bfs( int num , int* dist )
36 {
37     int ans , now , len;
38     len = -1;
39     memset( vis , false , sizeof(vis) );
40     queue<int>q;
41     q.push(num);
42     vis[num] = 1;
43     while( !q.empty() )
44     {
45         now = q.front();
46         q.pop();
47         if( dist[now] > len )
48         {
49             len = dist[now];
50             ans = now;
51         }
52         for( int i = head[now] ; ~i ; i = node[i].next )
53         {
54             int to = node[i].to;
55             int val = node[i].val;
56             if( !vis[to] )
57             {
58                 vis[to] = true;
59                 q.push(to);
60                 dist[to] = dist[now] + val;
61             }
62         }
63     }
64     return ans;
65 }
66 
67 int main()
68 {
69     cin.sync_with_stdio(false);
70     int n , x , y , point;
71     while( cin >> n )
72     {
73         cnt = 0;
74         init( );
75         for( int i = 2 ; i<=n ; i++ )
76         {
77             cin >> x >> y;
78             addEdge( i , x , y );
79             addEdge( x , i , y );
80         }
81         point = bfs( 1 , dist1 );
82         memset( dist1 , 0 , sizeof(dist1) );
83         point = bfs( point , dist1 );
84         point = bfs( point , dist2 );
85         for( int i = 1 ; i<=n ; i++ )
86         {
87             cout << max( dist1[i] , dist2[i] ) << endl;
88         }
89     }
90     return 0;
91 }