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80 lines
1.7 KiB
Markdown
80 lines
1.7 KiB
Markdown
---
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id: 691f7773cddba1caf1bf5eca
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title: "Challenge 131: Pairwise"
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challengeType: 29
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dashedName: challenge-131
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---
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# --description--
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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.
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For example, given `[2, 3, 4, 6, 8]` and `10`, you will find two valid pairs:
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- `2` and `8` (2 + 8 = 10), whose indices are `0` and `4`
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- `4` and `6` (4 + 6 = 10), whose indices are `2` and `3`
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Add all the indices together to get a return value of `9`.
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# --hints--
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`pairwise([2, 3, 4, 6, 8], 10)` should return `9`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(pairwise([2, 3, 4, 6, 8], 10), 9)`)
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}})
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```
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`pairwise([4, 1, 5, 2, 6, 3], 7)` should return `15`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(pairwise([4, 1, 5, 2, 6, 3], 7), 15)`)
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}})
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```
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`pairwise([-30, -15, 5, 10, 15, -5, 20, -40], -20)` should return `22`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(pairwise([-30, -15, 5, 10, 15, -5, 20, -40], -20), 22)`)
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}})
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```
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`pairwise([7, 9, 13, 19, 21, 6, 3, 1, 4, 8, 12, 22], 24)` should return `10`.
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```js
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({test: () => { runPython(`
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from unittest import TestCase
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TestCase().assertEqual(pairwise([7, 9, 13, 19, 21, 6, 3, 1, 4, 8, 12, 22], 24), 10)`)
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}})
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```
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# --seed--
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## --seed-contents--
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```py
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def pairwise(arr, target):
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return arr
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```
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# --solutions--
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```py
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def pairwise(arr, target):
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total = 0
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for i in range(len(arr)):
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for j in range(i + 1, len(arr)):
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if arr[i] + arr[j] == target:
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total += i + j
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return total
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```
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