154. Find Minimum in Rotated Sorted Array II
https://leetcode.com/problems/find-minimum-in-rotated-sorted-array-ii/
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.
(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).
Find the minimum element.
The array may contain duplicates.
Example 1:
Input: [1,3,5] Output: 1
Example 2:
Input: [2,2,2,0,1] Output: 0
Note:
- This is a follow up problem to Find Minimum in Rotated Sorted Array.
- Would allow duplicates affect the run-time complexity? How and why?
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Intuition
Standard binary search with unknown target
while (lo <= hi)
when lo == hi => infinite loop => terminate
Need to determine where pivot (minimum element) is relative to mid
if (nums[mid] < nums[hi])
=> mid to hi is strictly increasing
=> search in lower half
=> mid is min, potential ans, cannot discard
=> hi = mid
else if (nums[mid] > nums[hi])
=> pivot is somewhere between mid and hi
=> mid is higher element, discard it
=> lo = mid + 1
else
=> nums[mid] == nums[hi]
=> shrink search space, discarding hi still preserves mid as potential ans
=> eg [1, 1], [3, 3, 3, 1, 3]
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Time - O(log N)
Space - O(1)
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