Find missing number in an array given the sum

Here is the problem:

I have to code a program to solve an array. The number in the array that is not -1 are given, so I cannot change them.

N1 N2 N3
2 4 -1
1 -1 1
-1 8 -1

rowsum: 8, 9, 16
columnsum: 8 9 16

Firstly, what I did is search row1 for any -1 because by having only one -1 in the row, it means that is easily solvable. If 1x-1, Then I replace it with: row1sum-(row1N1+row1N2+row1N3).

Then I move on to the next row, checking if there is only 1x-1.
Then since row3 has 2 zeroes, I will not be able to work on that. So I skip it and check columnN1. If it only has 1x-1, then: columnN1 - (row1N1+row2N2+row3N3). Then column2, then column3.

My program worked with that problem but it doesn't with this:

n1 n2 n3
5 -1 -1
-1 7 -1
8 -1 0
rowsum: 14 19 16
columnsum: 22 15 7

Why doesn't my logic works? and if you have any suggestion on how to make this more efficient, I will gladly look into it :)

PS. It's my first month learning C, so I don't really have an advance knowledge.
PPS. I convert -1 to 0 first before adding.

> Why doesn't my logic works?
How should we know?
You didn't post your code.

Saying what you did is one thing.
Whether your program actually implements what you said is an entirely different matter.

You haven't even completely described the problem you're trying to solve. Are negative numbers allowed as answers? Presumably not, since -1 is used to indicate missing numbers. So I don't see how you can solve this (what is the answer?) :

Code:

---

.
 2  4 -1  | 8
 1 -1  1  | 9
-1  8 -1  |16
__________
 8  9 16

---

Also, the way you described your algorithm is obviously incorrect since it involves using the -1 in your calculation.

If I understand, the problem then you have bad data.

Because it is bad, when the sum of row sums do NOT equal the sum of column sums.

Edit: It looks like I do NOT understand the problem. Neither of the examples you posted are able to be solved by me; using what I think you say is the method.

Tim S.