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Find First and Last Position of Element in Sorted Array

medium

Given an array of integers nums sorted in non-decreasing order, find the starting and ending position of a given target value.

If target is not found in the array, return [-1, -1].

You must write an algorithm with O(log n) runtime complexity.

Test Cases

Copy an input into the main harness and Run to verify
Input
nums = [5,7,7,8,8,10], target = 8
Expected Output
[3,4]
Input
nums = [5,7,7,8,8,10], target = 6
Expected Output
[-1,-1]
Input
nums = [], target = 0
Expected Output
[-1,-1]

Constraints

  • 0 <= nums.length <= 10^5
  • -10^9 <= nums[i] <= 10^9
  • nums is sorted in non-decreasing order.
  • -10^9 <= target <= 10^9

Hints

Hint 1 — click to reveal

Once you find any occurrence, scanning outward is O(n) when the array is all the same value.

Hint 2 — click to reveal

Run binary search twice: once biased toward the left edge, once toward the right.

Java Compiler

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