Create longest-arithmetic-subsequence-of-given-difference.py

Author: kamyu104

Python/longest-arithmetic-subsequence-of-given-difference.py

@@ -0,0 +1,19 @@
+# Time:  O(n)
+# Space: O(n)
+
+import collections
+
+
+class Solution(object):
+    def longestSubsequence(self, arr, difference):
+        """
+        :type arr: List[int]
+        :type difference: int
+        :rtype: int
+        """
+        result = 1
+        lookup = collections.defaultdict(int)
+        for i in xrange(len(arr)):
+            lookup[arr[i]] = lookup[arr[i]-difference] + 1
+            result = max(result, lookup[arr[i]])
+        return result