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

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        
        start=0
        end=len(nums)-1

        while start<=end:
            
            mid=start + (end-start)//2
            
            if nums[mid]==target:
                return mid
            if target>nums[mid]:
                start=mid +1
            if target<nums[mid]:
                end=mid-1
                
        return -1