poj 1976 A Mini Locomotive

#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
int _,n,k;
int dp[4][50007],a[50007],b[50007];//dp[i][j]表示前i个火车头拉走前j个货箱
int dfs(int hc,int ed){
    if(hc<1||ed<1) return 0;
    if(dp[hc][ed]) return dp[hc][ed];
    return dp[hc][ed]=max(dfs(hc,ed-1),dfs(hc-1,ed-k)+b[ed]);//从这个位置用一个火车头拉走k个连续的货箱或者不管这个位置
}
int main(){
    freopen("1.in","r",stdin);
    freopen("1.out","w",stdout);
    scanf("%d",&_);
    while(_--){
        memset(dp,0,sizeof(dp));
        scanf("%d",&n);
        for(int i=1;i<=n;i++) scanf("%d",&a[i]);
        for(int i=2;i<=n;i++) a[i]+=a[i-1];a[0]=0;
        scanf("%d",&k);
        for(int i=k;i<=n;i++) b[i]=a[i]-a[i-k];
        printf("%d\n",dfs(3,n));
    }
    return 0;
}