Binary Search (LeetCode #704)

Challenge Statement

• Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.
• You must write an algorithm with O(log n) runtime complexity.
• This challenge corresponds to LeetCode #704.

Constraints

• 1 <= nums.length <= 104
• -104 < nums[i], target < 104
• All the integers in nums are unique.
• nums is sorted in ascending order.

Example 1:

Input: nums = [-1, 0, 3, 5, 9, 12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Example 2:

Input: nums = [-1, 0, 3, 5, 9, 12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

Example 3:

Input: head = []
Output: []

Solution

Below is my solution and some test cases. This solution has a logarithmic time complexity O(log n) and a constant space complexity O(1), where n is the length of the input list.