Binary Search

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.

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

Constraints:

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

SOLUTION:

class Solution: def search(self, nums: List[int], target: int) -> int: n = len(nums) beg = 0 end = n - 1 while beg <= end: mid = (beg + end) // 2 if nums[mid] == target: return mid elif beg == end: break elif nums[mid] > target: end = mid else: beg = mid + 1 return -1