Python describe LeetCode 81. Search rotation sort array II

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subject

It is known that there is an array of integers in non descending order nums , The values in the array don't have to be different from each other .

Before passing it to a function ,nums In some unknown subscript k（0 <= k < nums.length） On the rotate , Make array [nums[k], nums[k+1], ..., nums[n-1], nums[0], nums[1], ..., nums[k-1]]（ Subscript from 0 Start Count ）. for example , [0,1,2,4,4,4,5,6,6,7] In subscript 5 It may turn into [4,5,6,6,7,0,1,2,4,4] .

Here you are. After rotation Array of nums And an integer target , Please write a function to determine whether the given target value exists in the array . If nums There is a target value in target , Then return to true , Otherwise return to false .

You must minimize the whole procedure .

Example 1：

 Input ：nums = [2,5,6,0,0,1,2], target = 0
Output ：true

Example 2：

 Input ：nums = [2,5,6,0,0,1,2], target = 3
Output ：false

Tips ：

• 1 <= nums.length <= 5000
• -104 <= nums[i] <= 104
• Topic data assurance nums Rotated on a previously unknown subscript
• -104 <= target <= 104

Advanced ：

• This is a Search rotation sort array The extended topic of , In this question nums It may contain repeating elements .
• Does this affect the time complexity of the program ？ What kind of impact will it have , Why? ？

Python describe

Divided into two ordered sequences , Then two points

class Solution:
def search(self, nums: List[int], target: int) -> bool:
idx, n = 0, len(nums)
# Find the first position in reverse order 
while idx < n-1:
if nums[idx] > nums[idx+1]:
break
idx += 1
# Binary search in two ascending sequences target
l, r = 0, idx
while l <= r:
mid = l + r>> 1
if nums[mid] == target:
return True
elif nums[mid] < target:
l = mid + 1
else:
r = mid - 1
l, r = idx+1, n-1
while l <= r:
mid = l + r>> 1
if nums[mid] == target:
return True
elif nums[mid] < target:
l = mid + 1
else:
r = mid - 1
return False