Java recursion with one return statement

Question

Is it possible to add the numbers 1 to n recursively in Java with one return statement? How would you change the standard solution:

public static int sum(int n) {
   if(n == 1) return n;
    else return n + sum(n - 1);
}

Grégory Elhaimer · Accepted Answer · 2019-03-22 14:18:04Z

13

return n == 1 ? n : n + sum(n-1);

answered Mar 22, 2019 at 14:18

Grégory Elhaimer

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Comments

Lino · Accepted Answer · 2019-03-22 18:57:40Z

6

You could use simple maths without recursion:

public static int sum(int n) {
   return n * (n + 1) / 2;
}

edited Mar 22, 2019 at 18:57

answered Mar 22, 2019 at 14:22

Lino

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3 Comments

DCR Over a year ago

Wow, that’s an amazing formula did you figure that out yourself?

Lino Over a year ago

@DCR This problem has been known for quite a while, this formula is widely accessible on the internet

John Kugelman Over a year ago

If you want to get rid of the division use >> 1. There's no need to, though. The compiler will make this trivial optimization on its own. Exploiting integer overflow is bizarre.

Nicholas K · Accepted Answer · 2019-03-22 14:19:03Z

3

Yes, by making use of the ternary operator :

public static int sum(int n) {
    return n == 1 ? n : n + sum(n - 1);
}

answered Mar 22, 2019 at 14:19

Nicholas K

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Comments

Zeuzif · Accepted Answer · 2019-03-22 14:20:39Z

0

  public static int sum(int n) {
      return n == 1 ? 1 : n + sum(n-1);
  }

answered Mar 22, 2019 at 14:20

Zeuzif

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