Complete the solution so that it reverses the string passed into it
Complete the solution so that it reverses the string passed into it
This article was originally published on my blog
The reverse a string problem is a common algorithm problem. In this article, we will consider four JavaScript solutions to it.
A Little Background Info
Lately, I have been taking a course on data structures and algorithms. This is because I realized that I suck at it. This has not always been the case. When I started learning JavaScript, solving algorithm challenges was the fun part for me. I could stay up for hours late at night just trying to solve a challenge. But two years and many frontend projects later, it seems I’ve forgotten everything I learned. That is why I decided to go back to learn and practice.
Solid knowledge of data structures and algorithms comes with much practice. And what better way to remember what I learn that to write about it. That’s why I am presenting to you the first part of a series of articles to come.
Let’s delve into our algorithm challenge for today: Reversing a String
The Problem
Reversing a string is, well, reversing a string. Okay, here’s the problem statement: Write a function that reverses a string. If you pass «Sarah» to the function, it should return «haraS» and «listen» should become «netsil». Got it?
Now, let’s look at four javascript solutions.
Solution 1. Using the array reverse() method
Thanks to the Array.reverse() method, we can reverse an array without much stress. The reverse() method reverses an array in place. The first array element becomes the last, and the last array element becomes the first.
In our case though, we are working with strings. So this means that we have to convert the string to an array using the split method, reverse it using the reverse method and convert it back to a string using the join method. Here’s the code example.
Exit fullscreen mode
We can convert this to a one-liner using arrow function and implicit return.
Exit fullscreen mode
That’s it. One line of goodness. Let’s move to the next solution.
Solution 2: Good Ol’ For-loop
This is the classic example of reversing through a string. It might be one of the first methods that will come to your mind if you encounter this problem.
What we will do here is to create an empty string that will hold the reversed string, loop through each character in the string and append it to the beginning of the new string.
Exit fullscreen mode
The reduce() method executes a reducer function (that you provide) on each element of the array, resulting in single output value. You can read about it if you are not familiar with it.
Exit fullscreen mode
This function above can further be reduced to :
Exit fullscreen mode
Making it a one-liner and shortening the name of the variables used in the reduce method.
Exit fullscreen mode
Are you a friend of recursion? If not, let me introduce you to it.
Recursion is a way of solving a problem by using a function that calls itself. Each time the function calls itself, it reduces the problem into subproblems. This recursive call continues until a point is reached where the subproblem can be called without further recursion.
An important part of a recursive function is a base case. This is the condition(s) where the recursive call terminates to ensure it does not result in an infinite loop. You can find more explanations here.
Let’s get back to ‘reversing a string’. In this case, our base case is when the string is empty. We use the string.substring() method to get remove the first character in the string and pass the other characters to the function. Then we append the first character to our return statement as seen in the code below.
Exit fullscreen mode
We can use a ternary operator instead of if-else statements.
Exit fullscreen mode
Conclusion
So there you have it, four cools ways to reverse a string in JavaScript. Have any other solution to this problem, please share it in the comments. I would really love to know.
Got any question or feedback? please leave a comment.
Follow me on Instagram @sarah_codes_ where I regularly post software development tips and advice.
Развернуть все слова в строке
Write an application that reverses all the words of input text:
E.g. «abcd efgh» => «dcba hgfe»
All non-letter symbols should stay on the same places:
E.g. «a1bcd efg!h» => «d1cba hgf!e»
Use Latin alphabet for test onLy
Сам алгоритм я в принципе понимаю. Но не знаю как реализовать его. Ктт знает, напишите эту программку, да бы я разобрался в коде. Спасибо всем )
Развернуть в строке слова, разделенные произвольным числом пробелов
using System; using System.Linq; public static class Kata < public static string.
Как развернуть все предложения в строке?
Есть задача, по условию которой на вход принимаются несколько предложений, а на выход поступают эти.
В исходной строке а$ определить все слова, отличные от последнего слова. Вывести эти слова в столбик
Помогите решить: В исходной строке а$ определить все слова, отличные от последнего слова. Вывести.
int i = 0;
while(i 0
Да, я в курсе. Я имел в виду, конкретно для этого задания. Примерные масштабы для Java прилажухи я представить боюсь).
Добавлено через 2 минуты
а обязательно создавать Столько класснов, можно ведь написать намного приметивнее, как пишут новички, вроде меня. У тебя конечно, код оч красивый. Мне нравится, все так по полочкам разложено. Буду стремитсья к такому же))
Суть задачи не в решении ее, а в том, чтобы научить тебя писать чистый код, а мелкие задачи как раз подходят для этого.
Добавлено через 49 секунд
Можешь сделать все примитивнее и кинуть на проверку, тебе на код ревью скорее всего сделают 10 замечаний по написанию чистого кода)
Если не трудно, скажи, что ты вот это делал,
domino123, используй теги когда кидаешь код, на панели есть кнопочка Java
Добавлено через 5 минут
Как с помощью IndexOf выделить все слова в первой строке и сравнить их со словами во второй строке?
как с помощью IndexOf выделить все слова в первой строке и сравнить их со словами во второй строке.
Найти и сохранить в строке те слова, в которых есть хотя бы одна цифра. Все остальные слова удалить
Помогите пожалуйста, есть задачка: Дана строка. Словом текста считается любая последовательность.
Как заменить все слова в строке на слова?
регулярное выражение для замены всех слов в строке на слова
В заданной строке, слова которого разделены одним пробелом, напечатать все слова, содержащие заданную последовательность букв
В заданной строке, слова которого разделены одним пробелом, напечатать все слова, содержащие.
Найти в строке все одинаковые слова и удалить все повторения слов (+ блок схема)
Дана строка из произвольных слов. Найти все одинаковые слова и удалить все повторения слов.
Complete the solution so that it reverses the string passed into it
Copy raw contents
In this kata you get the start number and the end number of a region and should return the count of all numbers except numbers with a 5 in it. The start and the end number are both inclusive!
The result may contain fives. 😉 The start number will always be smaller than the end number. Both numbers can be also negative!
Complete the solution so that it reverses the string value passed into it.
In this Kata, you will remove the left-most duplicates from a list of integers and return the result.
Several people are standing in a row divided into two teams. The first person goes into team 1, the second goes into team 2, the third goes into team 1, and so on.
Given an array of positive integers (the weights of the people), return a new array/tuple of two integers, where the first one is the total weight of team 1, and the second one is the total weight of team 2.
Input >> Output Examples
The first element 62 is the total weight of team 1, and the second element 27 is the total weight of team 2.
The first element 120 is the total weight of team 1, and the second element 140 is the total weight of team 2.
The first element 80 is the total weight of team 1, and the second element 0 is the total weight of team 2.
In this Kata, you will be given a string and two indexes. Your task is to reverse the portion of that string between those two indices inclusive.
Input will be lowercase and uppercase letters only.
Complete the solution so that it reverses all of the words within the string passed in.
Given an array (arr) as an argument complete the function countSmileys that should return the total number of smiling faces.
Rules for a smiling face:
No additional characters are allowed except for those mentioned.
Valid smiley face examples: 🙂 😀 ;-D :
Invalid smiley faces: ;( :> :> :]
Note: In case of an empty array return 0. You will not be tested with invalid input (input will always be an array). Order of the face (eyes, nose, mouth) elements will always be the same
I have a cat and a dog.
I got them at the same time as kitten/puppy. That was humanYears years ago.
Return their respective ages now as [humanYears,catYears, dogYears]
Let’s create some scrolling text!
Your task is to complete the function which takes a string, and returns an array with all possible rotations of the given string, in uppercase.
In this Kata, we are going to reverse a string while maintaining spaces.
Complete the solution so that it reverses the string passed into it
Write a function called repeatString which repeats the given String src exactly count times.
首先想到的是 Array 、 Array.prototype.fill 和 Array.prototype.join 方法。但是看别人用的最多的是 String.prototype.repeat(n) 方法。
Complete the solution so that it reverses the string value passed into it.
利用 Array.prototype.reverse ，需要先将字符串转换为数组。
Because Nathan knows it is important to stay hydrated, he drinks 0.5 litres of water per hour of cycling.
You get given the time in hours and you need to return the number of litres Nathan will drink, rounded to the smallest value.
time = 6.7—> litres = 3
可以使用 parseInt 或者 Math.floor 静态方法进行向下取整，也可以利用逻辑运算隐式转换为整数。
Complete the square sum function so that it squares each number passed into it and then sums the results together.
Convert a String to a Number!
We need a function that can transform a string into a number. What ways of achieving this do you know?
Note: Don’t worry, all inputs will be strings, and every string is a perfectly valid representation of an integral number.
利用定义的转换函数，或者隐式的ToNumber转换。 parseInt 、 Number 、 +str 、 str|0 等操作。
Count the Monkeys!
You take your son to the forest to see the monkeys. You know that there are a certain number there (n), but your son is too young to just appreciate the full number, he has to start counting them from 1.
As a good parent, you will sit and count with him. Given the number (n), populate an array with all numbers up to and including that number, but excluding zero.
Complete the solution so that it reverses all of the words within the string passed in.
If you can’t sleep, just count sheep!!
If you can’t sleep, just count sheep!!
使用 Array.from 静态方法创建数组，提供映射函数，其中使用 Template Literals ，然后使用 Array.prototype.join 方法拼接。
Get the number n (n>0) to return the reversed sequence from n to 1.
To square(root) or not to square(root)
#To square(root) or not to square(root)
Write a method, that will get an integer array as parameter and will process every number from this array. Return a new array with processing every number of the input-array like this:
The input array will always contain only positive numbers and will never be empty or null.
The input array should not be modified!
Have fun coding it and please don’t forget to vote and rank this kata! 🙂
I have also created other katas. Take a look if you enjoyed this kata!
Get the Middle Character
You are going to be given a word. Your job is to return the middle character of the word. If the word’s length is odd, return the middle character. If the word’s length is even, return the middle 2 characters.
A word (string) of length 0 (In javascript you may get slightly more than 1000 in some test cases due to an error in the test cases). You do not need to test for this. This is only here to tell you that you do not need to worry about your solution timing out.
The middle character(s) of the word represented as a string.
利用 String.prototype.substr 方法。
An isogram is a word that has no repeating letters, consecutive or non-consecutive. Implement a function that determines whether a string that contains only letters is an isogram. Assume the empty string is an isogram. Ignore letter case.
n software engineering, the singleton pattern is a design pattern that restricts the instantiation of a class to one object. This is useful when exactly one object is needed to coordinate actions across the system.
Create an Singleton pattern, so there is one object in system.
Sum of Odd Cubed Numbers
Find the sum of the odd numbers within an array, after cubing the initial integers. The function should return undefined / None / nil / NULL if any of the values aren’t numbers.
筛选计算即可。不过这题了解到了逗号表达式的妙用。 return 只能当做语句而不能当做表达式，那样就能在三元运算符中使用了。
Currying functions: multiply all elements in an array
To complete this Kata you need to make a function multiplyAll / multiply_all which takes an array of integers as an argument. This function must return another function, which takes a single integer as an argument and returns a new array.
The returned array should consist of each of the elements from the first array multiplied by the integer.
Here’s a nice Youtube video about currying, which might help you if this is new to you.
使用 Array.prototype.map 函数进行映射。
global & ignore case。正则匹配。
Complete the code which should return true if the given object is a single ASCII letter (lower or upper case), false otherwise.
Implement the function which should return true if given object is a vowel (meaning a, e, i, o, u ), and false otherwise.
Hide password from jdbc url
We have to create a function that receives a connection string with password included and you have to mask the password i.e. change password by asterisks.
empty passwords are not validated but best solutions take empty passwords into account
正则匹配querystring的password部分，以 password 开头截止到 & 或者字符串尾结束。
You will be given an array of objects (hashes in ruby) representing data about developers who have signed up to attend the coding meetup that you are organising for the first time.
Your task is to return the number of JavaScript developers coming from Europe.
For example, given the following list:
Find the odd int
Given an array, find the integer that appears an odd number of times.
There will always be only one integer that appears an odd number of times.
Convert string to camel case
Complete the method/function so that it converts dash/underscore delimited words into camel casing. The first word within the output should be capitalized only if the original word was capitalized (known as Upper Camel Case, also often referred to as Pascal case).
使用正则表达式和 String.prototype.replace 。正则表达式匹配下划线和后续字母。 String.prototype.replace 参数如下：
Count the smiley faces!
) Invalid smiley faces: ;( :> :> :]
Example cases:
In case of an empty array return 0. You will not be tested with invalid input (input will always be an array). Order of the face (eyes, nose, mouth) elements will always be the same
Given a number, return a string with dash ‘-‘ marks before and after each odd integer, but do not begin or end the string with a dash mark.
Valid Phone Number
Write a function that accepts a string, and returns true if it is in the form of a phone number. Assume that any integer from 0-9 in any of the spots will produce a valid phone number.
Only worry about the following format: (123) 456-7890 (don’t forget the space after the close parentheses)
Your goal is to write an Event constructor function, which can be used to make event objects.
An event object should work like this:
As this is an elementary example of events, there are some simplifications:
Also see an example test fixture for suggested usage
观察者模式。使用 Set 来保存和删除添加的Handler。emit时调用所有注册的Handler。
A Chain adding function
We want to create a function that will add numbers together when called in succession.
We also want to be able to continue to add numbers to our chain.
A single call should return the number passed in.
We should be able to store the returned values and reuse them.
We can assume any number being passed in will be valid whole number.
通过观察上述 addTwo 函数既可以当数值也可以调用，因此可以通过 valueOf 方法返回所求数值。
This excercise is a more sophisticated version of Simple Events kata.
Your task is to implement an Event constructor function for creating event objects
which comply to the following:
an event object should have .subscribe() and .unsubscribe() methods to add and remove handlers
.subscribe() and .unsubscribe() should be able take an arbitrary number of arguments and tolerate invalid arguments (not functions, or for unsubscribe, functions which are not subscribed) by simply skipping them
multiple subscription of the same handler is allowed, and in this case unsubscription removes the last subscription of the same handler
an event object should have an .emit() method which must invoke all the handlers with the arguments provided
.emit() should use its own invocation context as handers’ invocation context
the order of handlers invocation must match the order of subscription
Check the test fixture for usage example
GamesOfSummer / Codewars-Reverse-String Goto Github PK
License: MIT License
JavaScript 32.90% TypeScript 67.10%
Codewars-Reverse-String’s Introduction
Complete the solution so that it reverses the string passed into it.
Oh. There is a reverse method. Huh. Guess I reinvented the wheel on that one.
Codewars-Reverse-String’s People
Contributors
Watchers
Recommend Projects
A declarative, efficient, and flexible JavaScript library for building user interfaces.
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
TensorFlow
An Open Source Machine Learning Framework for Everyone
Django
The Web framework for perfectionists with deadlines.
A PHP framework for web artisans
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
Recommend Topics
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
Some thing interesting about web. New door for the world.
server
A server is a program made to process requests and deliver data to clients.
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
Visualization
Some thing interesting about visualization, use data art
Some thing interesting about game, make everyone happy.
Recommend Org
We are working to build community through open source technology. NB: members must have two-factor auth.
Microsoft
Open source projects and samples from Microsoft.