Java > Recursion-1 > triangle (CodingBat Solution)

Problem:

We have triangle made of blocks. The topmost row has 1 block, the next row down has 2 blocks, the next row has 3 blocks, and so on. Compute recursively (no loops or multiplication) the total number of blocks in such a triangle with the given number of rows.

triangle(0) → 0
triangle(1) → 1
triangle(2) → 3


Solution:

public int triangle(int rows) {
  if (rows == 0) return 0;
  return rows + triangle(rows-1);
}

4 comments:

  1. AnonymousNovember 11, 2016 at 10:58 PM

    this is also the summation from i = 0 to i = n of i, so an alternative solution to the problem is simply n*(n+1)/2

    ReplyDelete
  2. UnknownMay 4, 2018 at 1:29 AM

    public int triangle(int rows) {
    return (rows ==0)? 0 : triangle(rows-1)+rows;
    }

    ReplyDelete
  3. fergcodyJanuary 8, 2019 at 3:10 PM

    same result

    public int triangle(int rows) {
    if(rows == 0) {
    return 0;
    }

    return rows + triangle(rows - 1);
    }

    ReplyDelete
  4. Flash_Investor_INJanuary 18, 2022 at 11:30 PM

    return rows==0?0:rows+triangle(rows-1);

    ReplyDelete