Rokua P1273 Cable TV network

2016-05-31 13:25:45

Topic Link: Rokua P1273 cable TV network

Main topic:

Take as many leaf nodes as possible on a given tree of weights, making sigma (val[selected leaf node])-sigma (cost[)) >=0

Solution:

Tree-like DP backpack DP

DP[I][J] represents the maximum profit obtained by selecting J leaf nodes for the subtree of the root of the I node.

Transfer equation

Dp[i][j]=max (Dp[i][j],dp[i][j-k]+dp[son][k]-cost[son][i]);

Places to be aware of

When writing the initial value, be aware that all but dp[i][0]=0 are-inf.

1 //Cable TV Network (Rokua no.1273)2 //tree-like DP backpack DP3#include <stdio.h>4#include <algorithm>5 using namespacestd;6 Const intmaxn=3010;7 intDP[MAXN][MAXN];8 structEdge9 {Ten     intto ; One     intCost ; A     intNext; - Edge () {} -EdgeintTo,intCostintnext): To, cost, next (next) {} the }; - Edge N[MAXN]; - intHEAD[MAXN]; - intCNT; + voidInsertintXintYintz) - { +n[++cnt]=Edge (Y,z,head[x]); Ahead[x]=CNT; at     return ; - } - intn,m; - intVAL[MAXN]; - intDasointx) - { in     if(x>n-M) -     { todp[x][1]=Val[x]; +         return 1; -     } the     intsum=0; *      for(intI=head[x];i;i=n[i].next) $     {Panax Notoginseng         intSize=DFS (n[i].to); -sum+=size; the          for(intj=sum;j>=0; j--) +         { A              for(intk=1; k<=size;k++) the             { +Dp[x][j]=max (dp[x][j],dp[x][j-k]+dp[n[i].to][k]-n[i].cost); -             } $         } $     } -     returnsum; - } the intMain () - {Wuyiscanf"%d%d",&n,&M); the      for(intI=0; i<maxn;i++) -     { WuFill (dp[i],dp[i]+maxn,-1000000); -     } About      for(intI=1; i<=n;i++) dp[i][0]=0; $      for(intI=1; i<=n-m;i++) -     { -         intx; -scanf"%d",&x); A          for(intj=1; j<=x;j++) +         { the             intTo,val; -scanf"%d%d",&to,&val); $ Insert (i,to,val); the         } the     } the      for(inti=n-m+1; i<=n;i++) the     { -scanf"%d",&val[i]); in     } theDFS (1); the      for(inti=m;i>=0; i--) About     { the         if(dp[1][i]>=0) the         { theprintf"%d", i); +             return 0; -         } the     }Bayi     return 0; the}

Rokua P1273 Cable TV network