freecodecamp--freecodecamp/curriculum/challenges/english/blocks/daily-coding-challenges-python/691f7773cddba1caf1bf5eca.md

id, title, challengeType, dashedName

id	title	challengeType	dashedName
691f7773cddba1caf1bf5eca	Challenge 131: Pairwise	29	challenge-131

--description--

Given an array of integers and a target number, find all pairs of elements in the array whose values add up to the target and return the sum of their indices.

For example, given [2, 3, 4, 6, 8] and 10, you will find two valid pairs:

• 2 and 8 (2 + 8 = 10), whose indices are 0 and 4
• 4 and 6 (4 + 6 = 10), whose indices are 2 and 3

Add all the indices together to get a return value of 9.

--hints--

pairwise([2, 3, 4, 6, 8], 10) should return 9.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(pairwise([2, 3, 4, 6, 8], 10), 9)`)
}})

pairwise([4, 1, 5, 2, 6, 3], 7) should return 15.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(pairwise([4, 1, 5, 2, 6, 3], 7), 15)`)
}})

pairwise([-30, -15, 5, 10, 15, -5, 20, -40], -20) should return 22.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(pairwise([-30, -15, 5, 10, 15, -5, 20, -40], -20), 22)`)
}})

pairwise([7, 9, 13, 19, 21, 6, 3, 1, 4, 8, 12, 22], 24) should return 10.

({test: () => { runPython(`
from unittest import TestCase
TestCase().assertEqual(pairwise([7, 9, 13, 19, 21, 6, 3, 1, 4, 8, 12, 22], 24), 10)`)
}})

--seed--

--seed-contents--

def pairwise(arr, target):

    return arr

--solutions--

def pairwise(arr, target):
    total = 0

    for i in range(len(arr)):
        for j in range(i + 1, len(arr)):
            if arr[i] + arr[j] == target:
                total += i + j

    return total