洛谷P1273 有线电视网 树上分组背包DP

#include <algorithm>
#include  <iterator>
#include  <iostream>
#include   <cstring>
#include   <cstdlib>
#include   <iomanip>
#include    <bitset>
#include    <cctype>
#include    <cstdio>
#include    <string>
#include    <vector>
#include     <stack>
#include     <cmath>
#include     <queue>
#include      <list>
#include       <map>
#include       <set>
#include   <cassert>

using namespace std;
#define lson (l , mid , rt << 1)
#define rson (mid + 1 , r , rt << 1 | 1)
#define debug(x) cerr << #x << " = " << x << "\n";
#define pb push_back
#define pq priority_queue



typedef long long ll;
typedef unsigned long long ull;
//typedef __int128 bll;
typedef pair<ll ,ll > pll;
typedef pair<int ,int > pii;
typedef pair<int,pii> p3;

//priority_queue<int> q;//这是一个大根堆q
//priority_queue<int,vector<int>,greater<int> >q;//这是一个小根堆q
#define fi first
#define se second
//#define endl ‘\n‘

#define OKC ios::sync_with_stdio(false);cin.tie(0)
#define FT(A,B,C) for(int A=B;A <= C;++A)  //用来压行
#define REP(i , j , k)  for(int i = j ; i <  k ; ++i)
#define max3(a,b,c) max(max(a,b), c);
#define min3(a,b,c) min(min(a,b), c);
//priority_queue<int ,vector<int>, greater<int> >que;

const ll mos = 0x7FFFFFFF;  //2147483647
const ll nmos = 0x80000000;  //-2147483648
const int inf = 0x3f3f3f3f;
const ll inff = 0x3f3f3f3f3f3f3f3f; //18
const int mod = 1e9+7;
const double esp = 1e-8;
const double PI=acos(-1.0);
const double PHI=0.61803399;    //黄金分割点
const double tPHI=0.38196601;


template<typename T>
inline T read(T&x){
    x=0;int f=0;char ch=getchar();
    while (ch<‘0‘||ch>‘9‘) f|=(ch==‘-‘),ch=getchar();
    while (ch>=‘0‘&&ch<=‘9‘) x=x*10+ch-‘0‘,ch=getchar();
    return x=f?-x:x;
}


/*-----------------------showtime----------------------*/
            const int maxn = 3009;
            vector<pii>mp[maxn];
            int n,m;
            int dp[maxn][maxn],a[maxn];
            int dfs(int u, int fa){
                int res = 0;

                if(mp[u].size() == 0) {
                    
                    dp[u][1] = a[u];
                    return 1;

                }
                for(int i=0; i<mp[u].size(); i++){
                    int v = mp[u][i].fi;
                    if(v == fa) continue;

                    res += dfs(v, u);
                    dp[u][0] = 0;
                    for(int j=res; j >= 1; j--){
                        for(int k=1; k<=j; k++){
                            dp[u][j] = max(dp[u][j], dp[u][j-k] + dp[v][k] - mp[u][i].se); 
                        }
                    }
                }
                return res;
            }

int main(){
            scanf("%d%d", &n, &m);
            memset(dp, ~inf, sizeof(dp));

            for(int i=1; i<=n-m; i++){
                    int k;  scanf("%d", &k);
                    for(int j=1; j<=k; j++) {
                        int v,w;
                        scanf("%d%d", &v, &w);
                        mp[i].pb(pii(v,w));
                    }
            }
            for(int i=n-m+1; i<=n; i++) scanf("%d", &a[i]);

            int tmp = dfs(1,-1);
            for(int i=tmp; i>=1; i--) {
                if(dp[1][i] >= 0) {
                    printf("%d\n", i);
                    return 0;
                }
            }
            return 0;
}