头一次遇到这样的前缀和，（看来是太菜了），自己一开始觉得是类似小根堆，然后发现是自己读题没读明白， 然后看了看，别人的写法， 学了学

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define iinf 0x3f3f3f3f
#define linf (1ll<<60)
#define eps 1e-8
#define maxn 1000010
#define maxe 1000010
#define cl(x) memset(x,0,sizeof(x))
#define rep(i,a,b) for(i=a;i<=b;i++)
#define drep(i,a,b) for(i=a;i>=b;i--)
#define em(x) emplace(x)
#define emb(x) emplace_back(x)
#define emf(x) emplace_front(x)
#define fi first
#define se second
#define pb push_back
#define de(x) cerr<<#x<<" = "<<x<<endl
#define __i __int128
using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll; 

ll read(ll x=0)
{
    ll c, f(1);
    for(c=getchar();!isdigit(c);c=getchar())if(c=='-')f=-f;
    for(;isdigit(c);c=getchar())x=x*10+c-0x30;
    return f*x;
}
int n , k, m ;
int cmp ( pll a, pll b){
    return a.first< b.first;
}
ll a[200010], sum[200010], f1[200010],f2[200010];
priority_queue<ll , vector<ll >  , greater<ll > > qe;
int main()
{
        ios::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);
       cin >> m;
       while(m--){
               cin >>n>>k;
               ll ans =-1e18;
        for(int i=1;i<=n;i++){
            cin>>a[i];
            sum[i]=a[i]+sum[i-1];
        }
         memset(f1,-0x3f3f3f3f,sizeof f1);memset(f2,-0x3f3f3f3f,sizeof f2);

        for(int i=k;i<=n-k;i++)
            f1[i]=max(sum[i]-sum[i-k],f1[i-1]);
        for(int i=n-k+1;i>=k+1;i--)
            f2[i]=max(sum[i+k-1]-sum[i-1],f2[i+1]);
        for(int i=k;i<=n-k;i++)
            ans=max(ans,f1[i]+f2[i+1]);
        cout<<ans<<endl;
       }
    return 0;
}