hdu 1011 树形背包

很显然是树形背包，注意m为0的情况。

#include <iostream>
#include <cstring>
#include <cstdio>
using namespace std;

const int N = 101;
int head[N];
int bn[N];
int value[N];
int dp[N][N];
int n, m, e;

struct Edge 
{
    int v, next;
} edge[N << 1];

void addEdge( int u, int v )
{
    edge[e].v = v;
    edge[e].next = head[u];
    head[u] = e++;
}

void dfs( int u, int fa )
{
    int tmp = ( bn[u] + 19 ) / 20;
    for ( int i = tmp; i <= m; i++ ) dp[u][i] = value[u];
    for ( int i = head[u]; i != -1; i = edge[i].next )
    {
        int v = edge[i].v;
        if ( v == fa ) continue;
        dfs( v, u );
        for ( int j = m; j >= tmp; j-- )
        {
            for ( int k = 1; j - k >= tmp; k++ )
            {
                dp[u][j] = max( dp[u][j], dp[u][j - k] + dp[v][k] );
            }
        }
    }
}

int main ()
{
    while ( scanf("%d%d", &n, &m) != EOF )
    {
        if ( n == -1 && m == -1 ) break;
        for ( int i = 1; i <= n; i++ )
        {
            scanf("%d%d", bn + i, value + i);
        }
        e = 0;
        memset( head, -1, sizeof(head) );
        for ( int i = 1; i < n; i++ )
        {
            int u, v;
            scanf("%d%d", &u, &v);
            addEdge( u, v );
            addEdge( v, u );
        }
        if ( !m )
        {
            puts("0");
            continue;
        }
        memset( dp, 0, sizeof(dp) );
        dfs( 1, -1 );
        printf("%d
", dp[1][m]);
    }
    return 0;
}