Workshop › Candy Crush-style Match 3 › Step 22 of 29

Is there any move?

What we are doing

A board can run out of moves: no swap makes a match. To know, try them all: swap each pair of neighbours, look, and swap back. hasMove returns the first move that works, or null.

```js
// Is there any swap that would make a match? Try each one, look, and swap back.
function hasMove() {
  for (let r = 0; r < N; r++) {
    for (let c = 0; c < N; c++) {
      for (const [dr, dc] of [[0, 1], [1, 0]]) {
        if (r + dr >= N || c + dc >= N) continue
        const a = { r, c }
        const b = { r: r + dr, c: c + dc }
        swap(a, b)
        const found = findMatches().size > 0
        swap(a, b)
        if (found) return { a, b }
      }
    }
  }
  return null
}
```

What it means

Each cell is paired with its right and lower neighbour; pairs that would leave the board are skipped.
Swap, remember whether there is a match, and always swap back, whatever was found.
The first move found is returned as { a, b }; if none, null.

Your turn

Write the comment and hasMove above function trySwap(a, b) {.

Skills: Loops, Game states

← Out from under the top Never stuck →

All steps