# Recursive Problem

**URL:** <https://discourse.processing.org/t/recursive-problem/19405>\
**Category:** Coding Questions\
**Created:** [April 4, 2020, 8:55pm UTC](https://discourse.processing.org/t/recursive-problem/19405 "2020-04-04T20:55:03Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![JudgeJesse](https://avatars.discourse-cdn.com/v4/letter/j/a3d4f5/32.png) [@JudgeJesse](https://discourse.processing.org/u/JudgeJesse)\
**Post date:** [April 4, 2020, 8:55pm UTC](https://discourse.processing.org/t/recursive-problem/19405/1 "2020-04-04T20:55:03Z")

</div>

Howdy! I’m trying to make a Sudoku Solver and I can’t seem to figure out this bug. I’ve got too many console.logs in here but you should be able see what’s happening. I use a recursive function to try all possible numbers but when it fails, I want it to backtrack through the stack, however when it backtracks it’s keeping the same indecies. Any idea what’s wrong? Thanks!

```auto
function solve() {
  for (jj = 0; jj < size; jj++) {
    for (ii = 0; ii < size; ii++) {
      if (grid[jj * size + ii].value == 0) {
        for (n = 1; n < size + 1; n++) {
          console.log('test (' + ii + ',' + jj + ') = ' + n)
          if (grid[jj * size + ii].possible(n)) {
            grid[jj * size + ii].value = n;
            console.log('(' + ii + '),(' + jj + ') set to ' +grid[jj * size + ii].value);
            redraw();
            solve();
            grid[jj * size + ii].value = 0;
            console.log('(' + ii + '),(' + jj + ') set to ' +grid[jj * size + ii].value);
            redraw();
          }
        }
        console.log('back track');
        return
      }
    }
  }
}

```

Console Log

```auto
test (2,0) = 1 

(2),(0) set to 1 

test (3,0) = 1 

test (3,0) = 2 

(3),(0) set to 2 

test (5,0) = 1 

test (5,0) = 2 

test (5,0) = 3 

test (5,0) = 4 

(5),(0) set to 4 

test (6,0) = 1 

test (6,0) = 2 

test (6,0) = 3 

test (6,0) = 4 

test (6,0) = 5 

test (6,0) = 6 

test (6,0) = 7 

test (6,0) = 8 

(6),(0) set to 8 

test (7,0) = 1 

test (7,0) = 2 

test (7,0) = 3 

test (7,0) = 4 

test (7,0) = 5 

test (7,0) = 6 

test (7,0) = 7 

test (7,0) = 8 

test (7,0) = 9 

(7),(0) set to 9 

test (8,0) = 1 

test (8,0) = 2 

test (8,0) = 3 

test (8,0) = 4 

test (8,0) = 5 

test (8,0) = 6 

test (8,0) = 7 

test (8,0) = 8 

test (8,0) = 9 

back track 

(8),(0) set to 0 

back track 

(8),(0) set to 0 

back track 

(8),(0) set to 0 

back track 

(8),(0) set to 0 

back track 

(8),(0) set to 0 

back track 

▶[Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell, Cell]

```

---

<div class="post-metadata">

**Author:** ![SomeOne](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.processing.org/someone/32/8639_2.png) [@SomeOne](https://discourse.processing.org/u/SomeOne)\
**Post date:** [April 6, 2020, 8:45am UTC](https://discourse.processing.org/t/recursive-problem/19405/2 "2020-04-06T08:45:43Z")

</div>

I don’t think that I have ever seen recursive function without a parameter. Actually I think it just cannot work. Parameters give function a state and recursion is based on that state.

I found a decent resource on recursion. It touches sudoku too: [https://www.cs.utah.edu/~germain/PPS/Topics/recursion.html](https://www.cs.utah.edu/~germain/PPS/Topics/recursion.html)

---

<div class="post-metadata">

**Author:** ![JudgeJesse](https://avatars.discourse-cdn.com/v4/letter/j/a3d4f5/32.png) [@JudgeJesse](https://discourse.processing.org/u/JudgeJesse)\
**Post date:** [April 6, 2020, 1:16pm UTC](https://discourse.processing.org/t/recursive-problem/19405/3 "2020-04-06T13:16:08Z")

</div>

Gotcha! I’ll have to review this thoroughly. My references was this video, which uses a recursive algorithm without a parameter:

[![](https://img.youtube.com/vi/G_UYXzGuqvM/maxresdefault.jpg "Python Sudoku Solver - Computerphile") ](https://www.youtube.com/watch?v=G_UYXzGuqvM)