01背包，买东西

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题目：

Description

Recently, iSea went to an ancient country. For such a long time, it was the most wealthy and powerful kingdom in the world. As a result, the people in this country are still very proud even if their nation hasn’t been so wealthy any more.
The merchants were the most typical, each of them only sold exactly one item, the price was Pi, but they would refuse to make a trade with you if your money were less than Qi, and iSea evaluated every item a value Vi.
If he had M units of money, what’s the maximum value iSea could get?

Input

There are several test cases in the input.

Each test case begin with two integers N, M (1 ≤ N ≤ 500, 1 ≤ M ≤ 5000), indicating the items’ number and the initial money.
Then N lines follow, each line contains three numbers Pi, Qi and Vi (1 ≤ Pi ≤ Qi ≤ 100, 1 ≤ Vi ≤ 1000), their meaning is in the description.

The input terminates by end of file marker.

Output

For each test case, output one integer, indicating maximum value iSea could get.

Sample Input

 2 1010 15 105 10 53 105 10 53 5 62 7 3

Sample Output

同学说这个题需要以价格和需要钱数的差值排序，我没有那样做，虽然过了，但是我觉得我这样做有问题。

代码：

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;struct node{int a;int b;int c;} ;bool cmp(node a,node b){if(a.b!=b.b) return a.b>b.b;return a.a<b.a;}bool cmp2(node a,node b){if(a.b!=b.b) return a.b<b.b;return a.a<b.a;}main(){int f[5010],f2[5010];int i;    struct node p[5550];int sum;int n,V,v;    while(scanf("%d%d",&n,&V)!=EOF){memset(f,0,sizeof(f));memset(f2,0,sizeof(f2));for(i=0;i<n;i++){scanf("%d%d%d",&p[i].a,&p[i].b,&p[i].c);}sort(p,p+n,cmp);for(i=0;i<n;i++){for(v=V;v>=p[i].b;v--){if(f[v]<f[v-p[i].a]+p[i].c)f[v]=f[v-p[i].a]+p[i].c;}}sort(p,p+n,cmp2);for(i=0;i<n;i++){for(v=V;v>=p[i].b;v--){if(f2[v]<f2[v-p[i].a]+p[i].c)f2[v]=f2[v-p[i].a]+p[i].c;}}if(f[V]>f2[V])sum=f[V];elsesum=f2[V];printf("%d\n",sum);}}

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