poj 1014 Dividing <多重背包>

链接：http://poj.org/problem?id=1014

题意： 价值为 i 的物品分别有 a[i] 个， 问是否能够均分。多重背包问题。

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
int a[10], M, dp[100000];
void zpack( int w, int v )
{
    for( int i=M; i>=w; -- i ){
        dp[i]=max(dp[i-w]+v, dp[i]);
    }
}

void cpack( int w, int v )
{
    for( int i=w; i<=M; ++ i ){
        dp[i]=max(dp[i-w]+v, dp[i]);
    }
}

int main( )
{
    int t=1;
    while( scanf( "%d", &a[1] )==1 ){
        int s=a[1];
        for( int i=2; i<=6; ++ i ){
            scanf( "%d", &a[i] );
            s+=i*a[i];
        }
        if( !s )break;
        if( s&1 ){
            printf( "Collection #%d:\nCan't be divided.\n\n", t++ );
            continue;
        }
        M=s/2;
        memset( dp, 0, sizeof dp );
        for( int i=1; i<=6;++ i ){
            if( i*a[i]>=M ){
                cpack( i, i );
            }
            else{
                int k=1; 
                while( k<=a[i] ){
                    zpack( k*i, k*i );
                    a[i]-=k;
                    k<<=1;
                }
                zpack( i*a[i], i*a[i] );
            }
        }
        if( dp[M]==M )    printf( "Collection #%d:\nCan be divided.\n\n", t++ );    
        else     printf( "Collection #%d:\nCan't be divided.\n\n", t++ );
    }
    return 0;
}