Create 1463-cherry-pickup-ii.kt

Author: a93a

kotlin/1463-cherry-pickup-ii.kt

@@ -0,0 +1,64 @@
+// DP top-dowm approach
+class Solution {
+    fun cherryPickup(grid: Array<IntArray>): Int {
+        val rows = grid.size
+        val cols = grid[0].size
+        var dp = Array (cols) { IntArray (cols) }
+
+        for (r in (rows - 1) downTo 0) {
+            val curDP = Array (cols) { IntArray (cols) }
+            for (c1 in 0 until cols) {
+                for (c2 in c1 + 1 until cols) {
+                    var max = 0
+                    val curPick = grid[r][c1] + grid[r][c2]
+                    for (c12 in arrayOf(-1, 0, 1)) {
+                        for (c22 in arrayOf(-1, 0, 1)) {
+                            val nC1 = c1 + c12
+                            val nC2 = c2 + c22
+                            if (nC1 < 0 || nC2 == cols) continue
+                            max = maxOf(
+                                max,
+                                curPick + dp[nC1][nC2]
+                            )
+                        }
+                    }
+                    curDP[c1][c2] = max
+                }
+            }
+            dp = curDP
+        }
+
+        return dp[0][cols - 1]
+    }
+}
+
+// Recursion + Memoization
+class Solution {
+    fun cherryPickup(grid: Array<IntArray>): Int {
+        val rows = grid.size
+        val cols = grid[0].size
+        val dp = HashMap<String, Int>()
+
+        fun dfs(r: Int, c1: Int, c2: Int): Int {
+            if (c1 == c2 || minOf(c1, c2) < 0 || maxOf(c1, c2) == cols) return 0
+            dp["$r:$c1:$c2"]?.let { return it }
+            if (r == rows - 1) return grid[r][c1] + grid[r][c2]
+
+            var res = 0
+            for (c12 in arrayOf(-1, 0, 1)) {
+                for (c22 in arrayOf(-1, 0, 1)) {
+                    res = maxOf(
+                        res,
+                        dfs(r + 1, c1 + c12, c2 + c22)
+                    )
+                }
+            }
+
+            res += grid[r][c1] + grid[r][c2]
+            dp["$r:$c1:$c2"] = res
+            return res
+        }
+
+        return dfs(0, 0, cols - 1)
+    }
+}