Poj2486 Apple Tree (Tree dp)

There is an apple tree. The u node on the tree contains num [u] apples. The root of the tree is node 1. king starts from the root, if you don't reach a node, you can eat up the apples at the point. Then, you can ask how many apples does king eat when there are no more than k steps.

There is an apple tree. The u node on the tree contains num [u] apples. The root of the tree is node 1. king starts from the root, if you don't reach a node, you can eat up the apples at the point. Then, you can ask how many apples does king eat when there are no more than k steps. Solution: Two dp arrays are processed. f1 [u] [I] indicates that, if step I is not exceeded, you can start from the u node, eat it down, and then return to the u node, the maximum number of apples you can eat. F2 [u] [I] indicates the maximum number of apples that can be eaten starting from the u node without exceeding step I.

Solution: Two dp arrays are processed. f1 [u] [I] indicates that, if step I is not exceeded, you can start from the u node, eat it down, and then return to the u node, the maximum number of apples you can eat. F2 [u] [I] indicates the maximum number of apples that can be eaten starting from the u node without exceeding step I.

#include<stdio.h>  #include<string.h>  #include<algorithm>  using namespace std ;  const int maxn = 111111 ;  int max ( int a , int b ) { return a > b ? a : b ; } int min ( int a , int b ) { return a < b ? a : b ; }  struct Edge {     int to , next ; } edge[maxn<<1]; int head[maxn] , tot , n , m ; int f1[111][2222]  , f2[111][222] , num[maxn] , ans , dis[1111] ;  void new_edge ( int a , int b ) {     edge[tot].to = b ;     edge[tot].next = head[a] ;     head[a] = tot ++ ;      edge[tot].to = a ;     edge[tot].next = head[b] ;     head[b] = tot ++ ; }  int c[111][222] , d[maxn] , l ;  void dfs ( int u , int fa , int *f ) {     int i , j , k ;     if ( u != 1 )     {         for ( i = dis[u] ; i <= m ; i ++ )             ans = max ( ans , f2[u][m-i] + f[i] ) ;     }      int fuck[222] ;     for ( i = head[u] ; i != -1 ; i = edge[i].next )     {         int v = edge[i].to ;         if ( v == fa ) continue ;          for ( j = 0 ; j <= m ; j ++ ) d[j] = 0 ;         int t = 0 ;         for ( j = head[u] ; j != -1 ; j = edge[j].next )         {             if ( edge[j].to == v || edge[j].to == fa ) continue;              t ++ ;             for ( k = 0 ; k <= m ; k ++ )                 c[t][k] = f1[edge[j].to][k] ;         }         for ( j = 1 ; j <= t ; j ++ )             for ( k = m ; k >= 0 ; k -- )                 for ( l = 0 ; l + 2 <= k ; l ++ )                     d[k] = max ( d[k] , d[k-l-2] + c[j][l]  ) ;          for ( j = 0 ; j <= m ; j ++ ) fuck[j] = 0 ;         for ( j = dis[u] ; j < m ; j ++ ) fuck[j+1] = f[j] ;         for ( j = dis[u] ; j <= m ; j ++ )             for ( k = 0 ; k <= m ; k ++ )                 if ( j + k + 1 <= m )                     fuck[j+k+1] = max ( fuck[j+k+1] , f[j] + d[k] + num[u] ) ;         dfs ( v , u , fuck ) ;     } }  void cal ( int u , int fa ) {     int i , j , k ;     for ( i = head[u] ; i != -1 ; i = edge[i].next )     {         int v = edge[i].to ;         if ( v == fa ) continue ;         dis[v] = dis[u] + 1 ;         cal ( v , u ) ;          for ( k = m ; k >= 0 ; k -- )             for ( j = 0 ; j + 2 <= k ; j ++ )                 f1[u][k] = max ( f1[u][k] , f1[u][k-j-2] + f1[v][j] ) ;           for ( k = 1 ; k <= m ; k ++ ) f2[u][k] = max ( f2[u][k] , f2[v][k-1] ) ;           for ( j = 0 ; j <= m ; j ++ ) d[j] = 0 ;         int t = 0 ;         for ( j = head[u] ; j != -1 ; j = edge[j].next )         {             if ( edge[j].to == v || edge[j].to == fa ) continue ;             t ++ ;             for ( k = 0 ; k <= m ; k ++ )                 c[t][k] = f1[edge[j].to][k] ;         }          for ( j = 1 ; j <= t ; j ++ )             for ( k = m ; k >= 0 ; k -- )                 for ( l = 0 ; l + 2 <= k ; l ++ )                     d[k] = max ( d[k] , d[k-l-2] + c[j][l]  ) ;          for ( j = 0 ; j <= m ; j ++ )             for ( k = 0 ; k + 1 <= j ; k ++ )                 f2[u][j] = max ( f2[u][j] , f2[v][k] + d[j-k-1] ) ;     }      for ( i = 0 ; i <= m ; i ++ ) f1[u][i] += num[u] , f2[u][i] += num[u] ;     for ( i = 1 ; i <= m ; i ++ ) f1[u][i] = max ( f1[u][i] , f1[u][i-1] ) , f2[u][i] = max ( f2[u][i] , f2[u][i-1] ) ; }  void init () {     int i ;     memset ( head , -1 , sizeof ( head ) ) ;     memset ( f1 , 0 , sizeof ( f1 ) ) ;     memset ( f2 , 0 , sizeof ( f2 ) ) ;     memset ( dis , 0 , sizeof ( dis ) ) ;     tot = ans = 0 ; }  int f[222] ; int main () {     int i , j , k , a , b ;     while ( scanf ( "%d%d" , &n , &m ) != EOF )     {         init () ;         for ( i = 1 ; i <= n ; i ++ ) scanf ( "%d" , &num[i] ) ;         for ( i = 1 ; i < n ; i ++ )         {             scanf ( "%d%d" , &a , &b ) ;             new_edge ( a , b ) ;         }         cal ( 1 , 0 ) ;         ans = f2[1][m] ;         for ( i = 0 ; i <= m ; i ++ ) f[i] = 0 ;         dfs ( 1 , 0 , f ) ;         printf ( "%d\n" , ans ) ;     } }