Sudoku: Difference between revisions
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9 6 7 4 1 5 3 2 8
2 5 3 6 9 8 4 1 7
</pre>
=={{header|Kotlin}}==
{{trans|C++}}
<lang scala>// version 1.2.10
class Sudoku(rows: List<String>) {
private val grid = IntArray(81)
private var solved = false
init {
require(rows.size == 9 && rows.all { it.length == 9 }) {
"Grid must be 9 x 9"
}
for (i in 0..8) {
for (j in 0..8 ) grid[9 * i + j] = rows[i][j] - '0'
}
}
fun solve() {
println("Starting grid:\n\n$this")
placeNumber(0)
println(if (solved) "Solution:\n\n$this" else "Unsolvable!")
}
private fun placeNumber(pos: Int) {
if (solved) return
if (pos == 81) {
solved = true
return
}
if (grid[pos] > 0) {
placeNumber(pos + 1)
return
}
for (n in 1..9) {
if (checkValidity(n, pos % 9, pos / 9)) {
grid[pos] = n
placeNumber(pos + 1)
if (solved) return
grid[pos] = 0
}
}
}
private fun checkValidity(v: Int, x: Int, y: Int): Boolean {
for (i in 0..8) {
if (grid[y * 9 + i] == v || grid[i * 9 + x] == v) return false
}
val startX = (x / 3) * 3
val startY = (y / 3) * 3
for (i in startY until startY + 3) {
for (j in startX until startX + 3) {
if (grid[i * 9 + j] == v) return false
}
}
return true
}
override fun toString(): String {
val sb = StringBuilder()
for (i in 0..8) {
for (j in 0..8) {
sb.append(grid[i * 9 + j])
sb.append(" ")
if (j == 2 || j == 5) sb.append("| ")
}
sb.append("\n")
if (i == 2 || i == 5) sb.append("------+-------+------\n")
}
return sb.toString()
}
}
fun main(args: Array<String>) {
val rows = listOf(
"850002400",
"720000009",
"004000000",
"000107002",
"305000900",
"040000000",
"000080070",
"017000000",
"000036040"
)
Sudoku(rows).solve()
}</lang>
{{out}}
<pre>
Starting grid:
8 5 0 | 0 0 2 | 4 0 0
7 2 0 | 0 0 0 | 0 0 9
0 0 4 | 0 0 0 | 0 0 0
------+-------+------
0 0 0 | 1 0 7 | 0 0 2
3 0 5 | 0 0 0 | 9 0 0
0 4 0 | 0 0 0 | 0 0 0
------+-------+------
0 0 0 | 0 8 0 | 0 7 0
0 1 7 | 0 0 0 | 0 0 0
0 0 0 | 0 3 6 | 0 4 0
Solution:
8 5 9 | 6 1 2 | 4 3 7
7 2 3 | 8 5 4 | 1 6 9
1 6 4 | 3 7 9 | 5 2 8
------+-------+------
9 8 6 | 1 4 7 | 3 5 2
3 7 5 | 2 6 8 | 9 1 4
2 4 1 | 5 9 3 | 7 8 6
------+-------+------
4 3 2 | 9 8 1 | 6 7 5
6 1 7 | 4 2 5 | 8 9 3
5 9 8 | 7 3 6 | 2 4 1
</pre>
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