1+ class Solution {
2+ 3+ data class State (val square : Int , val steps : Int )
4+ 5+ private fun findNextSquare (board : Array <IntArray >, square : Int ): Int {
6+ val n = board.size
7+ val row = n - (square - 1 ) / n - 1
8+ var column = (square - 1 ) % n
9+ 10+ if (row % 2 == n % 2 ) {
11+ column = n - 1 - column
12+ }
13+ 14+ return when {
15+ board[row][column] == - 1 -> square
16+ else -> board[row][column]
17+ }
18+ }
19+ 20+ fun snakesAndLadders (board : Array <IntArray >): Int {
21+ val n = board.size
22+ val lastSquare = n * n
23+ val visited = BooleanArray (lastSquare + 1 ) { false }
24+ val queue = LinkedList <State >().apply {
25+ push(State (1 , 0 ))
26+ }
27+ 28+ while (queue.isNotEmpty()) {
29+ val state = queue.pop()
30+ if (state.square == lastSquare) return state.steps
31+ 32+ for (i in 1 .. minOf(6 , lastSquare - state.square)) {
33+ val newSquare = findNextSquare(board, state.square + i)
34+ if (visited[newSquare]) continue
35+ 36+ queue.add(State (newSquare, state.steps + 1 ))
37+ visited[newSquare] = true
38+ }
39+ }
40+ 41+ return - 1
42+ }
43+ 44+ }
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