From f878952bbcb93d48850d9e20b1570c2a6bf32da0 Mon Sep 17 00:00:00 2001
From: Matej Focko <me@mfocko.xyz>
Date: Fri, 29 Nov 2024 22:09:20 +0100
Subject: [PATCH] =?UTF-8?q?kt:=20add=20=C2=AB2290.=20Minimum=20Obstacle=20?=
 =?UTF-8?q?Removal=20to=20Reach=20Corner=C2=BB?=
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URL:	https://leetcode.com/problems/minimum-obstacle-removal-to-reach-corner/
Signed-off-by: Matej Focko <me@mfocko.xyz>
---
 ...inimum-obstacle-removal-to-reach-corner.kt | 54 +++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 kt/minimum-obstacle-removal-to-reach-corner.kt

diff --git a/kt/minimum-obstacle-removal-to-reach-corner.kt b/kt/minimum-obstacle-removal-to-reach-corner.kt
new file mode 100644
index 0000000..81dc76e
--- /dev/null
+++ b/kt/minimum-obstacle-removal-to-reach-corner.kt
@@ -0,0 +1,54 @@
+class Solution {
+    private data class Position(val x: Int, val y: Int) {
+        operator fun plus(rhs: Position): Position = Position(x + rhs.x, y + rhs.y)
+    }
+
+    companion object {
+        private val DIRECTIONS =
+            listOf(
+                Position(0, 1),
+                Position(0, -1),
+                Position(1, 0),
+                Position(-1, 0),
+            )
+    }
+
+    private fun isValid(
+        grid: Array<IntArray>,
+        p: Position,
+    ): Boolean =
+        (
+            p.y >= 0 && p.y < grid.size && p.x >= 0 && p.x < grid[p.y].size
+        )
+
+    fun minimumObstacles(grid: Array<IntArray>): Int {
+        val (rows, cols) = grid.size to grid[0].size
+
+        val dp = Array(rows) { IntArray(cols) { Int.MAX_VALUE } }
+        dp[0][0] = 0
+
+        val deque = ArrayDeque<Pair<Position, Int>>()
+        deque.addLast(Position(0, 0) to 0)
+
+        while (!deque.isEmpty()) {
+            val (position, obstacles) = deque.removeFirst()
+
+            DIRECTIONS.forEach { dir ->
+                val next = position + dir
+                if (!isValid(grid, next) || dp[next.y][next.x] != Int.MAX_VALUE) {
+                    return@forEach
+                }
+
+                if (grid[next.y][next.x] == 1) {
+                    dp[next.y][next.x] = obstacles + 1
+                    deque.addLast(next to obstacles + 1)
+                } else {
+                    dp[next.y][next.x] = obstacles
+                    deque.addFirst(next to obstacles)
+                }
+            }
+        }
+
+        return dp[rows - 1][cols - 1]
+    }
+}