Binary search

left < right or left <= right

• <= because you gotta check that last value

How to calculate mid index?

• (left + right) // 2 could overflow if the indexes are huge
• left + half the distance between left and right
  • left + (right - left) // 2

def binary_search(arr, target):
    left = 0
    right = len(arr) - 1

    while (left <= right):
        mid = left + (right - left) // 2
        if arr[mid] == target:
            return mid
        if arr[mid] < target:
            left = mid + 1
        else:
            right = mid - 1

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Last update: 2023-04-24