Code snippet for medium post

concurrent_sudoku_solve.go

// Solve algorithm
func Solve(grid [N][N]int) (bool, [N][N]int) {
	ch := make(chan [N][N]int)

	pending, row, col := pendingPositions(grid)
	if !pending {
		fmt.Println("Solve calls:", count)
		return false, grid
	}

	// Let's try to find a solution for the pending position
	// in row and col. We will try with digits from 1 to 9
	for i := 1; i <= 9; i++ {
		if valid(grid, i, row, col) {
			grid[row][col] = i
			go recursiveSolution(grid, ch)
		}
	}

	select {
	case solution := <-ch:
		fmt.Println("Solve calls:", count)
		return true, solution
	default:
		return false, grid
	}
}