Workshop › Sudoku › Step 23 of 28

Hints

What we are doing

Stuck? H fills in a cell from the solution: the selected one if it is wrong or empty, otherwise the first cell that is. Hints are counted.

```js
let hints
  hints = 0

// A hint fills the selected cell (or the first empty one) from the solution.
function hint() {
  if (won) return
  let cell = grid[selected.r][selected.c] === solution[selected.r][selected.c] ? null : selected
  for (let i = 0; i < 81 && !cell; i++) {
    const r = Math.floor(i / 9)
    const c = i % 9
    if (grid[r][c] !== solution[r][c]) cell = { r, c }
  }
  if (!cell) return
  selected = cell
  grid[cell.r][cell.c] = solution[cell.r][cell.c]
  hints += 1
  checkWin()
}

  else if (event.key === 'h' || event.key === 'H') hint()
```

What it means

• If the selected cell already holds the right digit, cell starts as null and the loop looks for the first cell that differs from the solution.
• i < 81 && !cell stops the loop as soon as a cell is found.
• The hinted cell becomes selected, gets the right digit, and the hint is counted.

Your turn

1. Under let won, write let hints; in reset, set it to 0.
2. Under enter, write the comment and hint.
3. In keydown, add the H line at the end of the chain.

Skills: Game states, Keyboard and mouse input

← A new puzzle every game Best time →

All steps

1. Nine by nine
2. Lines and boxes
3. A puzzle from a string
4. The puzzle's own digits
5. Keep drawing
6. The selected cell
7. Light up row, column and box
8. The same digit everywhere
9. Click to select
10. Move with the arrows
11. Write digits
12. The three rules in one loop
13. Show mistakes
14. Solved!
15. A clock
16. The solved message
17. Play again
18. The easiest cell
19. The solver
20. Random order
21. Invent a puzzle
22. A new puzzle every game
23. Hints
24. Best time
25. N for a new puzzle
26. A number pad
27. Tap the pad
28. Build it yourself: undo