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110 lines
2.5 KiB
Markdown
110 lines
2.5 KiB
Markdown
---
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id: 69bc6cb30c1d112a2e110a08
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title: "Challenge 251: Array Sum Finder"
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challengeType: 29
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dashedName: challenge-251
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---
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# --description--
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Given an array of numbers and a target number, return the first subset of two or more numbers that adds up to the target.
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- The "first" subset is the one whose elements have the lowest possible indices, prioritizing the earliest index first.
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- Each number in the array may only be used once.
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- If no valid subset exists, return `"Sum not found"`.
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Return the matching numbers as an array in the order they appear in the original array.
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# --hints--
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`find_sum([1, 3, 5, 7], 6)` should return `[1, 5]`.
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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(find_sum([1, 3, 5, 7], 6), [1, 5])`)
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}})
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```
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`find_sum([1, 2, 3, 4, 5], 5)` should return `[1, 4]`.
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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(find_sum([1, 2, 3, 4, 5], 5), [1, 4])`)
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}})
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```
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`find_sum([1, 2, 3, 4, 5], 6)` should return `[1, 2, 3]`.
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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(find_sum([1, 2, 3, 4, 5], 6), [1, 2, 3])`)
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}})
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```
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`find_sum([-1, -2, 3, 4], 1)` should return `[-1, -2, 4]`.
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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(find_sum([-1, -2, 3, 4], 1), [-1, -2, 4])`)
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}})
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```
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`find_sum([3, 1, 4, 1, 5, 9, 2, 6], 10)` should return `[3, 1, 4, 2]`.
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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(find_sum([3, 1, 4, 1, 5, 9, 2, 6], 10), [3, 1, 4, 2])`)
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}})
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```
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`find_sum([1, 2, 3, 4, 5, 6, 7, 8, 9], 20)` should return `[1, 2, 3, 5, 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(find_sum([1, 2, 3, 4, 5, 6, 7, 8, 9], 20), [1, 2, 3, 5, 9])`)
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}})
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```
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`find_sum([7, 9, 4, 2, 5], 10)` should return `"Sum not found"`.
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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(find_sum([7, 9, 4, 2, 5], 10), "Sum not found")`)
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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 find_sum(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 find_sum(arr, target):
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def search(start, remaining, current):
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if remaining == 0 and len(current) >= 2:
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return current
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if start >= len(arr):
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return None
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for i in range(start, len(arr)):
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result = search(i + 1, remaining - arr[i], current + [arr[i]])
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if result is not None:
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return result
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return None
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return search(0, target, []) or "Sum not found"
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```
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