Create 1043-partition-array-for-maximum-sum.kt

Author: a93a

kotlin/1043-partition-array-for-maximum-sum.kt

@@ -0,0 +1,57 @@
+// Dp solution
+class Solution {
+    fun maxSumAfterPartitioning(arr: IntArray, k: Int): Int {
+        val n = arr.size
+        val dp = IntArray (k)
+        dp[0] = arr[0]
+
+        for (i in 1 until n) {
+            var curMax = 0
+            var maxAtI = 0
+            for (j in i downTo (i - k + 1)) {
+                if (j < 0) break
+
+                curMax = maxOf(curMax, arr[j])
+
+                val winLen = i - j + 1
+                val curSum = curMax * winLen
+                val subArrSum = if (j > 0) dp[(j - 1) % k] else dp[k - 1]
+
+                maxAtI = maxOf(maxAtI, curSum + subArrSum)
+            }
+
+            dp[i % k] = maxAtI
+        }
+
+        return dp[(n - 1) % k]
+    }
+}
+
+// recursion + memoization
+class Solution {
+    fun maxSumAfterPartitioning(arr: IntArray, k: Int): Int {
+        val n = arr.size
+        val dp = IntArray (n) { -1 }
+
+        fun dfs(i: Int): Int {
+            if (i == n) return 0
+            if (dp[i] != -1) return dp[i]
+
+            var curMax = 0
+            var res = 0
+            for (j in i until minOf(n, i + k)) {
+                curMax = maxOf(curMax, arr[j])
+                val winLen = j - i + 1
+                res = maxOf(
+                    res,
+                    dfs(j + 1) + curMax * winLen
+                )
+            }
+
+            dp[i] = res
+            return res
+        }
+
+        return dfs(0)
+    }
+}