Want to try solving this problem? You can submit your code online if you log in or register.

*
The problems in this set are designed to be more accessible to beginning coders. As a learning aid, walkthroughs discussing how to solve the problems in this set are available by clicking on this link.
On completion of this problem set, students should have experience at using arrays to store, search through, and manipulate large data sets.
*

**Input File:** `tripin.txt`

**Output File:** `tripout.txt`

**Time Limit:** 1 second

In this somewhat silly problem, you must write a program that reads in a list of non-negative integers and identifies all the 'triples' - the multiples of three. For the purposes of this problem, a triple is defined as *any* number that can be expressed in the form *(3 * integer)* - so 0 and 3 are also considered to be triples.

To make things a little more complicated, once you identify all the triples you will need to output their locations in the original list.

The first line of the input will consist of the single integer *n*, the number of integers in the list. (1 <= *n* <= 50,000)

Following this will be *n* lines describing the list, each containing a single integer between 0 and 2,000,000,000.

If there were any multiples of three in the list, the first line of your output should contain the single integer *k*, the number of triples found. The second line should contain *k* space-separated integers, describing the positions of the triples, in ascending order. (For example, if the 5^{th} number in the list is a triple, you should output "`5`".)

If there are no triples in the list at all, you are instead to output "`Nothing here!`" on a single line.

7 10 12 8 9 3 29 30

4 2 4 5 7

7 16 49 2 10 28 55 31

Nothing here!

In the first example, four of the integers in the list are triples: the 2^{nd}, 4^{th}, 5^{th} and 7^{th}. (Their values are 12 = 3x4, 9 = 3x3, 3 = 3x1, and 30 = 3x10.) In the second example there are no triples in the list.

The score for each input file will be 100% if the correct answer is written to the output file and 3% otherwise. Or maybe that was 0%.

Privacy
statement

© Australian Mathematics Trust 2001-2020

Page generated: 25 May 2020, 11:23am AEST