binary_serach_left_right

from random import *


def find_first(array, element): #[l, r) first entry element
    l = -1
    r = len(array)
    while l + 1 < r:
        m = (l + r)//2
        if array[m] >= element:
            r = m
        else:
            l = m
    return r # return array[r] - if need element, not index


def find_last(array, element): #(l, r] last entry element
    l = 0
    r = len(array)
    while l + 1 < r:
        m = (l + r)//2
        if array[m] > element:
            r = m
        else:
            l = m
    return l # return array[l] - if need element, not index


#a = [1, 2, 2, 3, 4, 5]
a = [randint(1, 4) for i in range(10)]
a.sort()
print(a)
print("index of first \"2\" in array:", find_first(a, 2))
print("index of last \"2\" in array:", find_last(a, 2))