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exklamationmark's solution

to Raindrops in the Go Track

Published at Jul 28 2018 · 0 comments
Test suite

Convert a number to a string, the contents of which depend on the number's factors.

  • If the number has 3 as a factor, output 'Pling'.
  • If the number has 5 as a factor, output 'Plang'.
  • If the number has 7 as a factor, output 'Plong'.
  • If the number does not have 3, 5, or 7 as a factor, just pass the number's digits straight through.


  • 28's factors are 1, 2, 4, 7, 14, 28.
    • In raindrop-speak, this would be a simple "Plong".
  • 30's factors are 1, 2, 3, 5, 6, 10, 15, 30.
    • In raindrop-speak, this would be a "PlingPlang".
  • 34 has four factors: 1, 2, 17, and 34.
    • In raindrop-speak, this would be "34".

No Stub

This may be the first Go track exercise you encounter without a stub: a pre-existing raindrops.go file for your solution. You may not see stubs in the future and should begin to get comfortable with creating your own Go files for your solutions.

One way to figure out what the function signature(s) you would need is to look at the corresponding *_test.go file. It will show you what the package level functions(s) should be that the test will use to verify the solution.

Running the tests

To run the tests run the command go test from within the exercise directory.

If the test suite contains benchmarks, you can run these with the --bench and --benchmem flags:

go test -v --bench . --benchmem

Keep in mind that each reviewer will run benchmarks on a different machine, with different specs, so the results from these benchmark tests may vary.

Further information

For more detailed information about the Go track, including how to get help if you're having trouble, please visit the exercism.io Go language page.


A variation on a famous interview question intended to weed out potential candidates. http://jumpstartlab.com

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


package raindrops

// Source: exercism/problem-specifications
// Commit: 99de15d raindrops: apply "input" policy
// Problem Specifications Version: 1.1.0

var tests = []struct {
	input    int
	expected string
	{1, "1"},
	{3, "Pling"},
	{5, "Plang"},
	{7, "Plong"},
	{6, "Pling"},
	{8, "8"},
	{9, "Pling"},
	{10, "Plang"},
	{14, "Plong"},
	{15, "PlingPlang"},
	{21, "PlingPlong"},
	{25, "Plang"},
	{27, "Pling"},
	{35, "PlangPlong"},
	{49, "Plong"},
	{52, "52"},
	{105, "PlingPlangPlong"},
	{3125, "Plang"},


package raindrops

import "testing"

func TestConvert(t *testing.T) {
	for _, test := range tests {
		if actual := Convert(test.input); actual != test.expected {
			t.Errorf("Convert(%d) = %q, expected %q.",
				test.input, actual, test.expected)

func BenchmarkConvert(b *testing.B) {
	for i := 0; i < b.N; i++ {
		for _, test := range tests {
package raindrops

import "strconv"

// Convert turns a number into a string, following the "raindrop" rule:
// - If the number has 3 as a factor, output 'Pling'.
// - If the number has 5 as a factor, output 'Plang'.
// - If the number has 7 as a factor, output 'Plong'.
// - If the number does not have 3, 5, or 7 as a factor,
//   just return it (as a string).
func Convert(n int) string {
	divisibleBy3 := n%3 == 0
	divisibleBy5 := n%5 == 0
	divisibleBy7 := n%7 == 0

	if !divisibleBy3 && !divisibleBy5 && !divisibleBy7 {
		return strconv.Itoa(n)

	res := ""
	if divisibleBy3 {
		res += "Pling"
	if divisibleBy5 {
		res += "Plang"
	if divisibleBy7 {
		res += "Plong"

	return res

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