Sum of all sub matrix using prefix/cumulative sum

#1

for( li=0; li <=max_row-1; li ++)

for(lj =0; lj <=max_col-1; lj ++)

 for(bi = li; bi <=max_row-1; bi++)

  for(bj=lj; bj<=max_col-1; bj++){
      
    sum+= arr[bi][bj] - arr[li-1][bj] - arr[bi][lj-1] + arr[li-1][lj-1];
      
  }

Sir told us this code but when li or lj will be equal to 0 then li-1 and lj-1 will become -1 and then arr[ li-1] will become arr[-1] which will give garbage value.
So how to resolve this??

#2

hello @abhayg1602
handle those cases separately using if statements.

use 0 for the array values if their indices are invalid.

#3

I have tried it but I am unable to get the answer please share the code

#4

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