add 1218

Author: Ashwagandha-coder

contest/src/main/java/com/github/contest/Execute.kt

@@ -1,7 +1,7 @@
 package com.github.contest
 
 
-import com.github.contest.dp.maxNonDecreasingLength
+import com.github.contest.dp.longestSubsequence
 import java.util.TreeMap
 
 
@@ -11,7 +11,7 @@ import java.util.TreeMap
 
 fun main() {
 
-    maxNonDecreasingLength(intArrayOf(11, 7, 7, 9), intArrayOf(19, 19, 1, 7))
+    longestSubsequence(intArrayOf(2, -6, -3, -6, 2, 0), -2).also { println(it) }
 }
 
 fun generateTesting() {

contest/src/main/java/com/github/contest/dp/DpLeetcode.kt

@@ -522,6 +522,25 @@ fun maxNonDecreasingLength(nums1: IntArray, nums2: IntArray): Int {
     return maxLen
 }
 
+/**
+ * 1218. Longest Arithmetic Subsequence of Given Difference
+ */
+
+
+fun longestSubsequence(arr: IntArray, difference: Int): Int {
+    val dp = mutableMapOf<Int, Int>()
+    var maxLen = 0
+
+    for (num in arr) {
+        val prev = num - difference
+        val len = dp.getOrDefault(prev, 0) + 1
+        dp[num] = len
+        maxLen = maxOf(maxLen, len)
+    }
+
+    return maxLen
+}
+