# Java Sudoku Solver Problem

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1. Mar 30, 2017

### Kaura

• Member warned to post directly in the thread, and give indication of warnings and behavior of program
I am attempting to create a Sudoku Solving Program in Java

This is what I have to far

https://pastebin.com/raw/tgnAGKb2

I have spent close to an hour trying to debug it but to no avail

Can someone more skilled than I please point me in the right direction?

2. Mar 30, 2017

### Staff: Mentor

What goes wrong where?
At which step does the program state deviate from your expectations?

3. Mar 30, 2017

### Kaura

It "solves" the Sudoku Board and outputs the solved board but there are repeats in the grids making the solution incorrect

4. Mar 30, 2017

### Staff: Mentor

Then you should check the function calls that incorrectly claim the assignment would be valid and see what goes wrong there.

5. Mar 30, 2017

### WWGD

Why not stop it at different points if possible, i.e., run just the first, say 10 lines and see where, at what step, the problem arises?

6. Mar 30, 2017

### Kaura

Yeah when I get the chance I might just try to debug it at every recursive call
Might take forever but it may be my last hope

7. Mar 30, 2017

### WWGD

Good luck, if you want help in the Math part, let us know ; unfortunately I am just a beginner programmer, tho others may be able to help you in that regard.

8. Mar 30, 2017

### ChrisVer

Code (Java):

for(int k = (row/3)*3; k < (row/3)*3+3; k++) {
for(int l = (col/3)*3; l < (col/3)*3+3; l++) {
if(k != row && l != col) {
if(b[row][col] == number) return false;
}
}

are you sure about that b[row][col] there? if yes, why are you even iterating over k and l? Hopefully this will solve it?
Also some additional stuff you can think about:
1) you could try to fix some lines where you're using hardcoding (such as the line where you check whether your column or row are above the size of the sudoku board). That's the reason you introduced SIZE in your class, no?
2) you could do use a continue statement within the for loops, since you have already checked the same rows and columns.. in other words, if you are in the top left corner [1]
[1][2][3]
[4][5][6]
[7][8][9]
when you reach the grid iteration you have:already check 2,3,4,7... you don't have to recheck them...
if you are at [5], you have already checked 4,6,2,8... etc...

Last edited: Mar 30, 2017
9. Mar 31, 2017

### willem2

Code (Text):
//check grids//
for(int k = (row/3)*3; k < (row/3)*3+3; k++) {
for(int l = (col/3)*3; l < (col/3)*3+3; l++) {
if(k != row && l != col) {
if(b[row][col] == number) return false;
}
}

That && should be an ||. If either (k!= row ) or (l != col) than the (k,l) cell differs from the (row,column) cell and you want to check for a duplicate.

10. Mar 31, 2017

### willem2

That doesn't matter, because you already checked the columns and rows. The output I get now is:

693857124
124569387
512473896
346791258
435928671
278346519
859214763
781632945
967185432

The problem is clearly with, the 3x3 boxes, since rows and colums have unique numbers.

.

11. Mar 31, 2017

### ChrisVer

did you check your grid iteration?

12. Mar 31, 2017

### Staff: Mentor

This should check b[k][l] (the loop variables), not b[row][col] (which is the place we want to validate itself).

13. Mar 31, 2017

### Kaura

Haha I knew I made some dumb mistake
Thank you so much for finding that
I switched b[row][col] with b[k][l] and the result looks fine now