RNQOJ [stupid]愚蠢的矿工(树形依赖背包)

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 3001, INF = 1e9 + 10;
inline int read() {
    char c = getchar(); int x = 0, f = 1;
    while(c < '0' || c > '9') {if(c == '-')f =- 1; c = getchar();}
    while(c >= '0' && c <= '9') x = x * 10 + c - '0', c = getchar();
    return x * f;
}
int N, M, w[MAXN], val[MAXN], siz[MAXN], rev[MAXN], f[MAXN][MAXN], tot = 0;
vector<int> v[MAXN];
void dfs(int x, int _fa) {
    rev[++tot] = x; siz[x] = 1;
    for(int i = 0, to; i < v[x].size(); i++) {
        if((to = v[x][i]) == _fa) continue;
        dfs(to, x);
        siz[x] += siz[to];
    }
}
main() {
    N = read(); M = read();
    for(int i = 1; i <= N; i++) val[i] = read(), w[i] = 1;
    for(int i = 1; i <= N; i++) {
        int x = read(), y = read();
        if(x == 0) continue;
        v[x].push_back(y); v[y].push_back(x);
    }
    dfs(1, 0);
    for(int i = N; i >= 1; i--) {
        for(int j = 0; j <= M; j++) {
            f[i][j] = f[i + siz[rev[i]]][j];
            if(j >= w[i]) f[i][j] = max(f[i][j], f[i + 1][j - w[rev[i]]] + val[rev[i]]);
        //  printf("%d %d %d\n", i, j, f[i][j]);
        }
    }
    cout << f[1][M];
}
/*
*/