Envío 2659

Código

#include <bits/stdc++.h>

#define fi first
#define se second
#define forn(i,n) for(int i=0; i< (int)n; ++i)
#define for1(i,n) for(int i=1; i<= (int)n; ++i)
#define fore(i,l,r) for(int i=(int)l; i<= (int)r; ++i)
#define ford(i,n) for(int i=(int)(n) - 1; i>= 0; --i)
#define fored(i,l,r) for(int i=(int)r; i>= (int)l; --i)
#define pb push_back
#define el '\n'
#define d(x) cout<< #x<< " " << x<<el
#define ri(n) scanf("%d",&n)
#define sz(v) ((int)v.size())
#define all(v) v.begin(),v.end()
#define allr(v) v.rbegin(),v.rend()

using namespace std;

typedef long long ll;
typedef double ld;
typedef pair<int,int> ii;
typedef pair<char,int> pci;
typedef tuple<int, int, int> tiii;
typedef pair<ll,ll> pll;
typedef vector<int> vi;

const int inf = 1e9;
const int nax = 1e5+200;
const ld pi = acos(-1);
const ld eps= 1e-9;

int dr[] = {1,-1,0, 0,1,-1,-1, 1};
int dc[] = {0, 0,1,-1,1, 1,-1,-1};

int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL); cout.tie(NULL);
  cout<< setprecision(20)<< fixed;
  int n, m;
  cin>> n>> m;
  vector<vector<int>> a(n, vector<int>(m,0)), pre;
  forn(i,n) forn(j,m) cin>> a[i][j];
  pre = a;

  forn(i,n){
    int sum = 0;
    forn(j,m){
      sum += pre[i][j];
      pre[i][j] = sum; 
    }
  }

  forn(j,m){
    int sum = 0;
    forn(i,n){
      sum += pre[i][j];
      pre[i][j] = sum; 
    }
  }
  int mx = a[0][0];
  forn(x1,n){
    forn(y1,m){
      fore(x2, x1, n-1){
        fore(y2, y1, m-1){
          int cur = pre[x2][y2];
          if(x1) cur -= pre[x1-1][y2];
          if(y1) cur -= pre[x2][y1-1];
          if(x1 && y1) cur += pre[x1-1][y1-1];
          mx = max(mx, cur);
        }
      }
    }
  }
  cout<< mx<<el;
}