Merge pull request #846 from hereisderek/main

130 surrounded-regions Kotlin solution

Author: Ahmad-A0

kotlin/130-Surrounded-Regions.kt

@@ -0,0 +1,45 @@
+package kotlin
+
+// Runtime: 356 ms, faster than 72.97% of Kotlin online submissions for Surrounded Regions.
+// Memory Usage: 48.5 MB, less than 75.68% of Kotlin online submissions for Surrounded Regions.
+// https://leetcode.com/submissions/detail/776042031/
+class Solution {
+    fun solve(board: Array<CharArray>): Unit {
+        val n = board.size
+        val m = board[0].size
+
+        for (y in 0 until n) {
+            for (x in 0 until m) {
+                if (x==0||x==m-1||y==0||y==n-1){
+                    if (board[y][x] == 'O') {
+                        markI(board, y, x)
+                    }
+                }
+            }
+        }
+
+        for (y in 0 until n) {
+            for (x in 0 until m) {
+                board[y][x] = when(board[y][x]){
+                    'O' -> 'X'
+                    'I' -> 'O'
+                    else -> board[y][x] // could've just 'continue'd only if leetcode uses newer version of Kotlin
+                }
+            }
+        }
+    }
+    fun inBound(board: Array<CharArray>, r: Int, c: Int) : Boolean {
+        val n = board.size
+        val m = board[0].size
+        return !(r < 0 || r >= n || c < 0 || c >= m)
+    }
+    fun markI(board: Array<CharArray>, y: Int, x: Int) {
+        if (!inBound(board, y, x)) return
+        if (board[y][x] != 'O') return
+        board[y][x] = 'I'
+        markI(board, y+1, x)
+        markI(board, y-1, x)
+        markI(board, y, x+1)
+        markI(board, y, x-1)
+    }
+}