Create 0909-snakes-and-ladders.kt

Author: a93a

kotlin/0909-snakes-and-ladders.kt

@@ -0,0 +1,37 @@
+class Solution {
+    fun snakesAndLadders(board: Array<IntArray>): Int {
+        val len = board.size
+        board.reverse()
+
+        fun intToPos(square: Int): Pair<Int, Int> {
+            val r = (square - 1) / len
+            var c = (square - 1) % len
+            if (r % 2 == 1)
+                c = len - 1 - c
+            return r to c
+        }
+
+        val q = LinkedList<Pair<Int, Int>>()
+        q.addFirst(1 to 0)
+        val visited = HashSet<Int>()
+        while (q.isNotEmpty()) {
+            val (square, moves) = q.removeLast()
+
+            for (i in 1..6) {
+                var next = i + square
+                val (r, c) = intToPos(next)
+                if (board[r][c] != -1)
+                    next = board[r][c]
+                if (next == len * len) 
+                    return moves + 1
+                if (next !in visited) {
+                    visited.add(next)
+                    q.addFirst(next to moves + 1)
+                }
+
+            }
+        }
+
+        return -1
+    }
+}