选课（背包类树形dp）

即在树上做背包

#include
#include
#include
using namespace std;

struct my{
       int next;
       int v;
};

const int maxn=1000+10;

int adj[maxn],fa,n,m,dp[maxn][maxn];
my bian[maxn*2];
int score[maxn];

void myinsert( int u, int v){
     bian[++fa].v=v;
     bian[fa].next=adj[u];
     adj[u]=fa;
}

void dfs( int x){
     dp[x][0]=0;
     for ( int i=adj[x];i!=-1;i=bian[i].next){
        int v=bian[i].v;
            dfs(v);
            for ( int t=m;t>=0;t--){
                for ( int j=t;j>=0;j--){
                        if (t-j>=0)
                    dp[x][t]=max(dp[x][t],dp[x][t-j]+dp[v][j]);
                }
            }
     }
     if (x!=0){
        for ( int t=m;t>0;t--){
            dp[x][t]=dp[x][t-1]+score[x];
        }
     }
}

int main(){
    int v;
    memset (adj,-1, sizeof (adj));
    memset (bian,-1, sizeof (bian));
    scanf ( "%d%d" ,&n,&m);
    for ( int i=1;i<=n;i++){
        scanf ( "%d%d" ,&v,&score[i]);
        myinsert(v,i);
      //  myinsert(i,v);
    }
    dfs(0);
    printf ( "%d" ,dp[0][m]);
return 0;
}

转载于:https://www.cnblogs.com/lmjer/p/9418929.html