Binary Search in Python

Binary search is a classic search algorithm that is commonly used to find a target value within a sorted list. It works by repeatedly dividing the list in half and discarding the half that is guaranteed not to contain the target.

Iterative Version

def binary_search(arr, target):
    low = 0
    high = len(arr) - 1
    while low <= high:
        mid = (low + high) // 2
        if arr[mid] < target:
            low = mid + 1
        elif arr[mid] > target:
            high = mid - 1
        else:
            return mid  # target found
    return -1  # target not found

Recursive Version

def recursive_binary_search(arr, target, low=0, high=None):
    if high is None:
        high = len(arr) - 1
    if low <= high:
        mid = (low + high) // 2
        if arr[mid] < target:
            return recursive_binary_search(arr, target, mid + 1, high)
        elif arr[mid] > target:
            return recursive_binary_search(arr, target, low, mid - 1)
        else:
            return mid  # target found
    return -1  # target not found

In both versions, the function will return the index of the target if it’s found in the list, and -1 if it’s not.