Daily Challenge #141 - Two Sum - DEV Community 👩‍💻👨‍💻

Write a function that takes an array of integers and a target number.

The function should find two different integers in the array that give the target value when added together. Return the indices in a tuple [e.g. (index1, index2)]. Some tests will have multiple solutions.

Test Cases
[1234,5678,9012], 14690
[1,2,3], 4
[2,2,3], 4
[5,10,15,20,25,30], 50

Happy coding!

This challenge comes from wthit56 on CodeWars. Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

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Scala

def solve (xs: Seq[Int], target: Int): Option[(Int, Int)] = {
  val indexed = xs zip (0 until xs.size)

  @tailrec
  def solveRec (xs: Seq[(Int, Int)]): Option[(Int, Int)] =
    xs match {
      case Nil            => None
      case (x, i) :: rest =>
        rest find {
          case (y, j) => x + y == target
        } match {
          case None         => solveRec(rest)
          case Some((y, j)) => Some((i, j))
        }
    }
  solveRec(indexed)
}

And the tests

class PairsumTest extends FunSuite {
  test("solve") {
    assert(solve(List(1234,5678,9012), 14690) == Some((1, 2)))
    assert(solve(List(1,2,3), 4) == Some((0, 2)))
    assert(solve(List(2,2,3), 4) == Some((0, 1)))
    assert(solve(List(5,10,15,20,25,30), 50) == Some((3, 5)))
    assert(solve(List(), 23) == None)
    assert(solve(List(5, 14, 38), 23) == None)
  }
}

def two_sum(a, target) a .each_with_index .to_a .combination(2) .inject([]) { |r, ((a, i1), (b, i2))| r << [i1, i2] if a + b == target ; r } end two_sum([1234,5678,9012], 14690) #=> [[1, 2]] two_sum([5,10,15,20,25,30], 50) #=> [[3,5]]

// Corrected solution const func = (arr, sum) => arr .map((x, i) => [x, i]) .map(([x1, i1], _, a) => [i1, a.findIndex(([x2, i2]) => i1 !== i2 && x1 + x2 === sum)]) .find(([i1, i2]) => i2 !== -1);

fn two_sum(numbers: &[i64], target: i64) -> Option<(usize, usize)> { let mut complete_with = std::collections::HashMap::new(); for (idx1, &num) in numbers.iter().enumerate() { if let Some(&idx2) = complete_with.get(&(target - num)) { return Some((idx1, idx2)); } else { complete_with.insert(num, idx1); } } None } fn main() { for (numbers, target) in &[ (vec![1234, 5678, 9012], 14690), (vec![1, 2, 3], 4), (vec![2, 2, 3], 4), (vec![5, 10, 15, 20, 25, 30], 50), ] { if let Some((idx1, idx2)) = two_sum(numbers, *target) { assert!(numbers[idx1] + numbers[idx2] == *target); } } }

Daily Challenge #141 - Two Sum

dev.to staff Dec 22 '19 ・1 min read

dev.to staff

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