I am trying to apply an effective divide and conquer approach on a 2D array that is sorted row-wise, and column-wise. Starting from the bottom left cell in the matrix, my algorithm chooses either to move one cell up or one cell to right depending on whether k is > or < than the curr_cell. However, I keep getting an error of **list_indices out of range** when I run this code. I’d like some help in debugging this.

The following is my code:

```
def KeyFinder(k, matrix, x, y):
curr_cell = matrix[x][y] #starting at bottom left corner
if k == curr_cell:
return curr_cell
else:
if curr_cell < k:
KeyFinder(k, matrix, x-1, y) #if target is less than value, it must be above us so move one up
else:
KeyFinder(k, matrix, x, y+1) #otherwise, move one right
var = KeyFinder(20, [[1,4,7,11], [8,9,10,20], [11,12,17,30]], 2, 0)
print(var)
```

### >Solution :

For the error that you see, you have to check the bounds in both direction, not to go out of your matrix.

However, aprart from that your implementation has other issues like when you are calling you function recursively you are not returning the answer.

I did fix it like this:

```
def KeyFinder(k, matrix, x, y):
m, n = len(matrix) , len(matrix[0]) # get you dimentions
curr_cell = matrix[x][y] #starting at bottom left corner
if k == curr_cell:
return curr_cell
if curr_cell > k and (0 < x) :
return KeyFinder(k, matrix, x-1, y) #if target is less than value, it must be above us so move one up
elif (y < n - 1) :
return KeyFinder(k, matrix, x, y+1) #otherwise, move one right
var = KeyFinder(20, [[1,4,7,11], [8,9,10,20], [11,12,17,30]], 2, 0)
print(var)
```

I did not change the way you wrote to be easy for you to see the changes, however, when you get the dimension you can as well set the starting point inside the function, not in the call