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exklamationmark's solution

to Reverse String in the Go Track

Published at Jul 13 2018 · 0 comments
Test suite


This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Reverse a string

For example: input: "cool" output: "looc"

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.


Introductory challenge to reverse an input string https://medium.freecodecamp.org/how-to-reverse-a-string-in-javascript-in-3-different-ways-75e4763c68cb

Submitting Incomplete Solutions

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


package reverse

// Source: exercism/problem-specifications
// Commit: 2f77985 reverse-string: apply "input" policy
// Problem Specifications Version: 1.1.0

type reverseTestCase struct {
	description string
	input       string
	expected    string

var testCases = []reverseTestCase{
		description: "an empty string",
		input:       "",
		expected:    "",
		description: "a word",
		input:       "robot",
		expected:    "tobor",
		description: "a capitalized word",
		input:       "Ramen",
		expected:    "nemaR",
		description: "a sentence with punctuation",
		input:       "I'm hungry!",
		expected:    "!yrgnuh m'I",
		description: "a palindrome",
		input:       "racecar",
		expected:    "racecar",


package reverse

import (

func TestReverse(t *testing.T) {
	for _, testCase := range append(testCases, multiByteCases...) {
		if res := String(testCase.input); res != testCase.expected {
			t.Fatalf("FAIL: %s(%s)\nExpected: %q\nActual: %q",
				testCase.description, testCase.input, testCase.expected, res)
		t.Logf("PASS: %s", testCase.description)

func TestReverseOfReverse(t *testing.T) {
	assertion := func(s string) bool {
		return s == String(String(s))
	if err := quick.Check(assertion, nil); err != nil {

func BenchmarkReverse(b *testing.B) {
	for i := 0; i < b.N; i++ {
		for _, test := range testCases {

// mutiByteCases adds UTF-8 multi-byte case,
// since the canonical-data.json (generator data source for cases_test.go)
// doesn't have any such cases.
var multiByteCases = []reverseTestCase{
		description: "a multi-byte test case",
		input:       "Hello, 世界",
		expected:    "界世 ,olleH",
package reverse

func String(str string) string {
	runes := []rune(str)

	for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
		runes[i], runes[j] = runes[j], runes[i]

	return string(runes)

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