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First and Last Position of Element
Certification: Basic Level
Accuracy: 0%
Submissions: 0
Points: 5
Write a JavaScript program to find the first and last position of a target element in a sorted array. Given a sorted array of integers and a target value, return the starting and ending position of the target element. If the target is not found in the array, return [-1, -1]. The algorithm must run in O(log n) time complexity.
Example 1
- Input: nums = [5, 7, 7, 8, 8, 10], target = 8
- Output: [3, 4]
- Explanation:
- The sorted array is [5, 7, 7, 8, 8, 10].
- Target element 8 appears at indices 3 and 4.
- First occurrence of 8 is at index 3, last occurrence of 8 is at index 4.
- Return [3, 4] as the result.
- The sorted array is [5, 7, 7, 8, 8, 10].
Example 2
- Input: nums = [5, 7, 7, 8, 8, 10], target = 6
- Output: [-1, -1]
- Explanation:
- The sorted array is [5, 7, 7, 8, 8, 10].
- Target element 6 is searched in the array.
- 6 is not present in the array.
- Since target is not found, return [-1, -1].
- The sorted array is [5, 7, 7, 8, 8, 10].
Constraints
- 0 ≤ nums.length ≤ 10^5
- -10^9 ≤ nums[i] ≤ 10^9
- nums is a non-decreasing array
- -10^9 ≤ target ≤ 10^9
- Time Complexity: O(log n)
- Space Complexity: O(1)
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Solution Hints
- Use binary search to achieve O(log n) time complexity
- Perform two separate binary searches: one for first position, one for last position
- For finding first position, when target is found, continue searching in left half
- For finding last position, when target is found, continue searching in right half
- Handle edge cases where target is not present in the array
- Return [-1, -1] if target is not found