first_and_last_position.py

def find_start(arr, target):
    if arr[0] == target:
        return 0
    left, right = 0, len(arr)-1
    while left <= right:
        mid = (left+right)//2
        if arr[mid] == target and arr[mid-1] < target:
            return mid
        elif arr[mid] < target:
            left = mid+1
        else:
            right = mid-1
    return -1


def find_end(arr, target):
    if arr[-1] == target:
        return len(arr)-1
    left, right = 0, len(arr)-1
    while left <= right:
        mid = (left+right)//2
        if arr[mid] == target and arr[mid+1] > target:
            return mid
        elif arr[mid] > target:
            right = mid-1
        else:
            left = mid+1
    return -1


def first_and_last(arr, target):
    if len(arr) == 0 or arr[0] > target or arr[-1] < target:
        return [-1, -1]
    start = find_start(arr, target)
    end = find_end(arr, target)
    return [start, end]


if __name__ == '__main__':
    arr = [2, 4, 5, 5, 5, 5, 5, 7, 9, 9]
    target = 5

    print(first_and_last(arr, target))

    # Output:
    # [2, 6]