master-algorithms-py/searching/find_pair_nums.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# author: bt3gl


def bs(array, item):

    start, end = 0, len(array)
    mid = (end - start) // 2

    while len(array) > 0:
        if array[mid] == item:
            return True
        elif array[mid] > item:
            return bs(array[mid + 1:], item)
        else:
            return bs(array[:mid], item)
    
    return False
    

def find_pairs_bs(array, desired_sum):

    for i in range(len(array)):
        num1 = array[i]
        desired_num = desired_sum - num1
        if bs(array[i + 1:], desired_num) == True:
            return (num1, desired_num)

    return False


def find_pairs_max_sum(array, desired_sum):

    i, j = 0, len(array) - 1

    while i < j:
        this_sum = array[i] + array[j]
        if this_sum == desired_sum:
            return array[i], array[j]
        elif this_sum > desired_sum:
            j -= 1
        else:
            i += 1
            
    return False
    

def find_pairs_not_sorted(array, desired_sum):

    lookup = {}

    for item in array:
        key = desired_sum - item

        if key in lookup.keys():
            lookup[key] += 1
        else:
            lookup[key] = 1

    for item in array:
        key = desired_sum - item

        if item in lookup.keys():
            if lookup[item] == 1: 
                return (item, key)
            else:
                lookup[item] -= 1

    return False



if __name__ == "__main__":

    desired_sum = 8
    array1 = [1, 2, 3, 9]
    array2 = [1, 2, 4, 5, 4]
    array3 = [2, 1, 6, 3, 11, 2]

    assert(find_pairs_bs(array1, desired_sum) == False)
    assert(find_pairs_bs(array2, desired_sum) == (4, 4))
    assert(find_pairs_max_sum(array1, desired_sum) == False)
    assert(find_pairs_max_sum(array2, desired_sum) == (4,4))
    assert(find_pairs_not_sorted(array1, desired_sum) == False)
    assert(find_pairs_not_sorted(array2, desired_sum) == (4, 4))
    assert(find_pairs_not_sorted(array3, desired_sum) == (2, 6))