Create 1911-maximum-alternating-subsequence-sum.kt

Author: a93a

kotlin/1911-maximum-alternating-subsequence-sum.kt

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+class Solution {
+    fun maxAlternatingSum(nums: IntArray): Long {
+        val dp = Array (2) { LongArray (nums.size) { -1L } }
+
+        fun dfs(i: Int, even: Int): Long {
+            if (i == nums.size)
+                return 0
+            if (dp[even][i] != -1L)
+                return dp[even][i]
+
+            var sum = if (even == 1) nums[i] else -1 * nums[i]
+            dp[even][i] = maxOf(
+                sum + dfs(i + 1, if (even == 1) 0 else 1),
+                dfs(i + 1, even)
+            )
+
+            return dp[even][i]
+        }
+
+        return dfs(0, 1)
+    }
+}