这咋回事

#include<bits/stdc++.h>
using namespace std;
long long dp[200005],x[100005],v[100005];
int main()
{
	freopen("medicine.in","r",stdin);
	freopen("medicine.out","w",stdout);
	int t;
	scanf("%d",&t);
	while(t--)
	{
		memset(dp,0,sizeof dp);
		int n,V;
		scanf("%d%d",&n,&V);
		for(int i=1;i<=n;i++)
		      scanf("%lld%lld",&x[i],&v[i]);
		for(int i=1;i<=n;i++)
		    for(int j=V;j>=x[i];j--)
		        dp[j]=max(dp[j],dp[j-x[i]]+v[i]);
		 printf("%lld\n",dp[V]);
	}
}