LC_Binary_Search.py

"""
704. 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.
"""

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