Hint/Approach for problem

Hi, please provide any hint or approcach to solve this problem?

Just take prefix sum of every row and after that take prefix sum of every column.
Then if you partition the (i,j)th of grid then your top-left box sum will be the value at (i,j)th index of grid
and top-right box sum will be the sum at that row’s last column - the sum of top-left box sum
and bottom right box sum will be the value at (n,j)th of grid - the sum of top-left box
and bottom-right box sum will be the value at (n,m)th of grid - top-right box sum - bottom left box sum + the sum of top-left box ( because it get subtracted two times , first time in top-right box sum and second time in bottom-left box sum ).
Make ans at every step as
ans = max ( ans, min( all four boxes) );
For code reference you can have a look at the code shared on the link below:

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