HDU 1712 ACboy needs your help

该题是一道分组背包题；

题意就是ACboy发最多M的时间能够得到最多效益；输入有N没课程，没门课程发费j天得到的效益是map[i][j]；

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int map[124][124];
inline int Max( int a , int b )
{
    return a > b ?  a : b;       
}
int DP( int N , int M  )
{
    int f[124][124] ={ 0 };
    for( int i = 1 ; i <= N ; i ++ )
    {
        for( int j = 1 ; j <= M ; j++  )
           for( int  k = M ; k >= j ; k-- )
           {
              f[i][k] = Max( f[i][k] ,f[i-1][k] );
              f[i][k] = Max( f[i][k] , f[i-1][k-j] + map[i][j] );     
           }     
    }
    return f[N][M];
}
int main(  )
{
    int N ,M ;
    while( scanf( "%d%d",&N ,& M ), N||M )
    {
        for( int i = 1 ; i <= N; i++ ) 
           for( int j = 1 ; j <= M ; j++ )
             scanf( "%d" ,&map[i][j] );
        printf( "%d\n", DP(  N ,M  ) );      
    }
    return 0;    
}