Link
Solution
dp，拿线段树维护
Code
#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 20010
#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 de(x) cerr<<#x<<" = "<<x<<endl
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;
}
struct SegmentTree
{
ll mn[maxn<<2], mx[maxn<<2], sum[maxn<<2], add[maxn<<2], set[maxn<<2], L[maxn<<2], R[maxn<<2];
void maketag_set(ll o, ll v)
{
add[o]=0;
set[o]=v;
mx[o]=mn[o]=v;
sum[o]=(R[o]-L[o]+1)*v;
}
void maketag_add(ll o, ll v)
{
add[o]+=v;
mx[o]+=v, mn[o]+=v;
sum[o]+=(R[o]-L[o]+1)*v;
}
void pushdown(ll o)
{
if(L[o]==R[o])return;
if(~set[o])
{
maketag_set(o<<1,set[o]);
maketag_set(o<<1|1,set[o]);
set[o]=-1;
}
if(add[o])
{
maketag_add(o<<1,add[o]);
maketag_add(o<<1|1,add[o]);
add[o]=0;
}
}
void pushup(ll o)
{
mx[o]=max(mx[o<<1],mx[o<<1|1]);
mn[o]=min(mn[o<<1],mn[o<<1|1]);
sum[o]=sum[o<<1]+sum[o<<1|1];
}
void build(ll o, ll l, ll r, ll* array=NULL)
{
ll mid(l+r>>1);
L[o]=l, R[o]=r;
add[o]=0;
set[o]=-1;
if(l==r)
{
if(array)mn[o]=mx[o]=sum[o]=array[l];
else mn[o]=mx[o]=sum[o]=0;
return;
}
build(o<<1,l,mid,array);
build(o<<1|1,mid+1,r,array);
pushup(o);
}
void Set(ll o, ll l, ll r, ll v)
{
ll mid(L[o]+R[o]>>1);
if(l<=L[o] and r>=R[o]){maketag_set(o,v);return;}
pushdown(o);
if(l<=mid)Set(o<<1,l,r,v);
if(r>mid)Set(o<<1|1,l,r,v);
pushup(o);
}
void Add(ll o, ll l, ll r, ll v)
{
ll mid(L[o]+R[o]>>1);
if(l<=L[o] and r>=R[o]){maketag_add(o,v);return;}
pushdown(o);
if(l<=mid)Add(o<<1,l,r,v);
if(r>mid)Add(o<<1|1,l,r,v);
pushup(o);
}
ll Sum(ll o, ll l, ll r)
{
pushdown(o);
ll mid(L[o]+R[o]>>1), ans(0);
if(l<=L[o] and r>=R[o])return sum[o];
if(l<=mid)ans+=Sum(o<<1,l,r);
if(r>mid)ans+=Sum(o<<1|1,l,r);
return ans;
}
ll Min(ll o, ll l, ll r)
{
ll mid(L[o]+R[o]>>1), ans(linf);
if(l<=L[o] and r>=R[o])return mn[o];
pushdown(o);
if(l<=mid)ans=min(ans,Min(o<<1,l,r));
if(r>mid)ans=min(ans,Min(o<<1|1,l,r));
return ans;
}
ll Max(ll o, ll l, ll r)
{
ll mid(L[o]+R[o]>>1), ans(-linf);
if(l<=L[o] and r>=R[o])return mx[o];
pushdown(o);
if(l<=mid)ans=max(ans,Max(o<<1,l,r));
if(r>mid)ans=max(ans,Max(o<<1|1,l,r));
return ans;
}
}segtree;
ll a[55][maxn], f[maxn], g[maxn], s[55][maxn];
int main()
{
ll n=read(), m=read(), k=read(), i, j;
rep(i,1,n)rep(j,1,m)a[i][j]=read();
rep(i,1,n)rep(j,1,m)s[i][j]=s[i][j-1]+a[i][j];
rep(j,1,m-k+1)f[j] = (s[1][j+k-1]-s[1][j-1]) + (s[2][j+k-1]-s[2][j-1]);
rep(i,2,n)
{
rep(j,1,m-k+1)
{
g[j] = f[j];
if(j<=k)g[j] -= s[i][k] - s[i][j-1];
}
segtree.build(1,1,m-k+1,g);
rep(j,1,m-k+1)
{
f[j] = segtree.Max(1,1,m-k+1) + (s[i][j+k-1]-s[i][j-1]) + (s[i+1][j+k-1]-s[i+1][j-1]);
segtree.Add(1,max(1ll,j-k+1),j,a[i][j]);
if(j<m-k+1)segtree.Add(1,j+1,j+k,-a[i][j+k]);
}
}
ll ans=0;
rep(j,1,m-k+1)ans=max(ans,f[j]);
printf("%lld",ans);
return 0;
}