Create [CLOSED]LEET0376_WIGGLE_SUBSEQUENCE.py

[CLOSED]LEET0376_WIGGLE_SUBSEQUENCE.py

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+'''
+A sequence of numbers is called a wiggle sequence if the differences between successive numbers strictly alternate between positive 
+and negative. The first difference (if one exists) may be either positive or negative. 
+A sequence with fewer than two elements is trivially a wiggle sequence. For example, [1,7,4,9,2,5] is a wiggle sequence because the differences (6,-3,5,-7,3) are alternately positive and negative. In contrast, [1,4,7,2,5] and [1,7,4,5,5] are not wiggle sequences, the first because its first two differences are positive and the second because its last difference is zero.Given a sequence of integers, return the length of the longest subsequence that is a wiggle sequence. A subsequence is obtained by deleting some number of elements (eventually, also zero) from the original sequence, leaving the remaining elements in their original order.Examples:Input: [1,7,4,9,2,5]
+Output: 6
+The entire sequence is a wiggle sequence.
+
+Input: [1,17,5,10,13,15,10,5,16,8]
+Output: 7
+There are several subsequences that achieve this length. One is [1,17,10,13,10,16,8].
+
+Input: [1,2,3,4,5,6,7,8,9]
+Output: 2
+'''
+
+def wiggleMaxLength(L):
+  L=[L[i] for i in range(len(L)) if L[i]!=L[i-1] or i==0]
+  if len(L)<=1:
+    return len(L)
+  def length(L):
+    count=2
+    for i in range(2,len(L)):
+      if (L[i]-L[i-1])*(L[i-1]-L[i-2])<0:
+      count+=1
+    return count
+  return max(length(L),length(L[1:]))
+
+'''
+O(n) time, O(1) extra space
+'''