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Find the Index of a Target in a Sorted Array of Distinct Integers

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MediumSoftware EngineerOnsiteCoding & Algorithms

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Practice locating a target value in a strictly increasing array of distinct integers, returning its zero-based index or -1 when it is absent. The task checks logarithmic-time search over sorted data, precise loop boundaries, and correct handling of single-element arrays and values that fall between or outside the stored elements.

Given an array nums of distinct integers sorted in strictly increasing order and an integer target, return the position of target in nums. If target is not present, return -1.

Function Signature

def find_target_index(nums: list[int], target: int) -> int:

Rules

  • Positions are 0-based: the first element of nums is at index 0.
  • Because the values in nums are distinct, target appears at most once, so the returned index is unique.
  • Return -1 if and only if target does not occur in nums.
  • Do not modify nums.
  • The algorithm must run in $O(\log n)$ time, where $n$ is the length of nums.

Constraints

  • 1 <= len(nums) <= 10^4
  • -10^4 < nums[i] < 10^4 for every index i
  • -10^4 < target < 10^4
  • nums[i] < nums[i + 1] for every 0 <= i < len(nums) - 1 (strictly increasing, so there are no duplicates)
  • All values are well within the 32-bit signed integer range.

Examples

Example 1

Input: nums = [-7, -2, 0, 4, 11, 15], target = 4
Output: 3

nums[3] is 4.

Example 2

Input: nums = [-7, -2, 0, 4, 11, 15], target = 5
Output: -1

5 would fall between 4 and 11, but it is not in the array.

Example 3

Input: nums = [8], target = 8
Output: 0

The only element is the target.