Java Sudoku solver not producing correct output

[Kaura]

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?

 

[mfb]

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

 

[Kaura]

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

 

[mfb]

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

 

[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?

 

[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

 

[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.

 

[ChrisVer]

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...

 

[willem2]

//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.

 

[willem2]

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.

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.

.

 

[ChrisVer]

did you check your grid iteration?

 

[mfb]

if(b[row][col] == number) return false;

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

 

[Kaura]

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

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...

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