CODEWITHSUNDEEP
python
ewe
ewe

Reputation: 159

solving a easy python challenge with for in loops

"""
Given a list of numbers and a number k, return whether any two numbers from the list add up to k.

For example, given [10, 15, 3, 7] and k of 17, return true since 10 + 7 is 17.

"""
numbers = [7, 15, 17]
k = 14

def add_to_k(numbers_list,k_value):
    truth = False
    for i in numbers_list:
        for l in numbers_list:
            added = i + l
            if added == k_value:
                num1 = i
                num2 = l
                truth = True
    if truth == True:
        print("Two numbers in the list added together is 17. " + str(num1) + " " + str(num2))
    else:
        print("Sorry, none give " + str(k_value))
add_to_k(numbers,k)

Following the prompt in the comments above, I made my attempt at this challenge. However, I realized that it would add the first number of the list twice, though I want to find two separate numbers that would add up to k. How would I go about changing this code? Thank you!

Upvotes: 0

Views: 190

Answers (3)

cdlane
cdlane

Reputation: 41872

Let's try a simple approach with no additional libraries. But we will exploit Python's new walrus := operator:

def add_to_k(numbers, k):
    pairs = []

    while numbers:
        if (b := k - (a := numbers.pop())) in numbers:
            pairs.append((a, b))
            numbers.remove(b)

    return pairs

if __name__ == "__main__":
    numbers = [10, 15, 2, 7]

    k = 17

    if pairs := add_to_k(numbers, k):
        for pair in pairs:
            print("{} + {} = {}".format(*pair, k))
    else:
        print("Sorry, no solution for {}".format(k))

OUTPUT

> python3 test.py
7 + 10 = 17
2 + 15 = 17
>

In addition to finding multiple solutions if they exist, the result of this add_to_k() can also be treated as a boolean to say whether any solution exists. This solution should handle problems like k = 18 and numbers = [9, 9] vs. numbers = [9] correctly.

Upvotes: 0

MrNobody33
MrNobody33

Reputation: 6483

You should iterate over the array without the element that is being tested:

numbers = [7, 7, 17]
k = 14

def add_to_k(numbers_list,k_value):
    truth = False
    for i in numbers_list:
        y = numbers_list[:]  # fastest way to copy
        y.remove(i)
        for l in y:
            added = i + l
            if added == k_value:
                num1 = i
                num2 = l
                truth = True
    if truth == True:
        print("Two numbers in the list added together is "+str(k_value)+ ":  " + str(num1) + "," + str(num2))
    else:
        print("Sorry, none give " + str(k_value))
add_to_k(numbers,k)

Output:

 Two numbers in the list added together is 14:  7,7

Or if want another option:

import itertools as it
numbers = [12, 7, 17]
k = 19

def add_to_k(numbers_list,k_value):
    results = {i:sum(i) for i in list(it.combinations(numbers_list, 2))}
    if any(val==k_value for val in results.values()):
        print(f'Two numbers in the list added together is {k_value}:{list(results.keys())[list(results.values()).index(k_value)] }')
    else:
        print(f'Sorry, none give {k_value}')
    
add_to_k(numbers,k)

Output

Two numbers in the list added together is 19:(12, 7)

Upvotes: 3

Red
Red

Reputation: 27567

You can use combinations from itertools:

from itertools import combinations

numbers = [7, 15, 17, 10, 4]
k = 14

for t in combinations(numbers,2):
    if sum(t)==k:
        print(f"Two numbers in the list added together is {k}. {t[0]} {t[1]}")
        break
else:
    print(f"Sorry, none give {k}")

Output:

Two numbers in the list added together is 14. 10 4

Upvotes: 1

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