step

SudokuBacktracking.groovy

    void step() {
        if (isFixedNumber["$rowIndex$columnIndex" as String]) {
            nextCell()
        } else {
            int cell = board[rowIndex][columnIndex]
            int value = ++cell
            if (value <= 9) {
                board[rowIndex][columnIndex] = value
                if (this.isValid()) {
                    nextCell()
                }
            } else {
                board[rowIndex][columnIndex] = 0
                do {
                    previousCell()
                } while (isFixedNumber["$rowIndex$columnIndex" as String])
            }
        }
        printTable()
    }