poj 2392 Space Elevator

Description
The cows are going to space! They plan to achieve orbit by building a sort of space elevator: a giant tower of blocks. They have K (1 <= K <= 400) different types of blocks with which to build the tower. Each block of type i has
height h_i (1 <= h_i <= 100) and is available in quantity c_i (1 <= c_i <= 10). Due to possible damage caused by cosmic rays, no part of a block of type i can exceed a maximum altitude a_i (1 <= a_i <= 40000).

Help the cows build the tallest space elevator possible by stacking blocks on top of each other according to the rules.
Input
* Line 1: A single integer, K

* Lines 2..K+1: Each line contains three space-separated integers: h_i, a_i, and c_i. Line i+1 describes block type i.
Output
* Line 1: A single integer H, the maximum height of a tower that can be built
http://poj.org/problem?id=2392
 
代码：多重背包

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define max	40010
#define Max(a,b)	a > b ? a : b
#define Min(a,b)	a < b ? a : b

typedef struct a
{
int height;
int altitude;
int count;
}Block;
Block	block[max];
int dp[max];

int cmp(const void *a, const void *b)
{
Block *blocka = (Block *)a;
Block *blockb = (Block *)b;
if(blocka->altitude != blockb->altitude)
return blocka->altitude - blockb->altitude;
}
int main()
{
int k;
while(scanf("%d",&k) != EOF)
{
memset(dp,0,sizeof(0));
for(int i = 0; i < k; i++)
scanf("%d %d %d",&block[i].height,&block[i].altitude,&block[i].count);
qsort(block,k,sizeof(block[0]),cmp);
for(int i = 0; i < k; i++)
{
for(int m = 1; m <= block[i].count; m++)
for(int j = block[i].altitude; j >= block[i].height; j--)
{
dp[j] = Max(dp[j],dp[j - block[i].height] + block[i].height);
}
}
int max_H = 0;
for(int i = 0; i <= block[k - 1].altitude; i++)
max_H = Max(max_H, dp[i]);
printf("%d\n",max_H);
}
}