Reversing the order of a string value - swift

Question

I have the following function which reverses a string value's display order.
I'm new to Swift and I'm trying to understand it's logic. What is going on with the '!pleh' value that it turns into 'Help!' ?
Thanks
func reverse(_ s: String) -> String {
var str = ""
for character in s.characters {
str = "\(character)" + str
}
return str
}
print (reverse("!pleH"))

Answer 1

In swift 4.0, directly call reversed on a string will get the job done
let str = "abc"
String(str.reversed()) // This will give you cba

Answer 2

Commented inline,
func reverse(_ s: String) -> String {
var str = ""
//.characters gives the character view of the string passed. You can think of it as array of characters.
for character in s.characters {
str = "\(character)" + str
//This will help you understand the logic.
//!+""
//p+!
//l+p! ... goes this way
print ( str)
}
return str
}
print (reverse("!pleH"))

Answer 3

Note: If you don't want to use the reversed() in-built function, then you can use the following code.
One-liner using Higher-order function "Reduce" on the string.
extension String {
func reverse() -> String { return self.reduce("") { "\($1)" + $0 } }
}

Answer 4

The function reversed(_:) iterates over each Character in the supplied string s, and simply concenates them in the reverse order.
// 1st pass in the 'for' loop:
// # start of iteration: 'str' equals ""
// update value of 'str' according to
// str = aCharacterAsString + str = "!" + ""
// 2nd pass in the 'for' loop:
// # start of iteration: str equals "!"
// update value of 'str' according to
// str = anotherCharacterAsString + str = "p" + "!"
// 3rd pass in the 'for' loop:
// # start of iteration: str equals "p!"
// update value of 'str' according to
// str = yetAnotherCharacterAsString + str = "l" + "p!"
// and so on ...
// after end of 'for' loop: str == "help!"
// this value of 'str' is then return to callee (which prints it)
A much simpler approach would be using reversed() on the CharacterView of the String instance:
let str = "!pleH"
print(String(str.characters.reversed())) // Help!
Swift 4 You can use it directly in your string
let str = "!pleH"
print(String(str.reversed())) // Help!

Answer 5

var string = "My,playground and my Swift"
var reverseString = ""
for str in string {
reverseString.insert(str, at: reverseString.startIndex)
}
print(reverseString)

Answer 6

In Swift 4 - To reverse string ::
func reverse(string:String) -> String {
var reverse = ""
for char in string {
reverse = char.description + reverse
}
return reverse
}
Input :: reverse(string: "Ashish Chhabra")
Output :: arbahhC hsihsA

Answer 7

var strnew = "hello world new"
var reverseStr = ""
for each in strnew
{
reverseStr = String(each) + reverseStr
}
print(reverseStr)

Answer 8

Different variation of answer using Character and Index.
//Reverse String
func reverse(str:String)->String{
var chars = [Character]()
for i in (0...str.count).reversed() {
let index = str.index(str.startIndex, offsetBy: i)
chars.append(str[index])
}
return String(chars)
}

Answer 9

You can use below code-
let str = "My name is Kplin Cours"
var reverseString = ""
for i in 0..<str.count {
let index = str.index(str.startIndex, offsetBy: (str.count - 1) - i)
// print(String(str[index]))
reverseString = reverseString + String(str[index])
}
print(reverseString) //sruoC nilpK si eman yM

Answer 10

let string = readLine()!
var resultString = ""
for i in 1...string.count {
let index = string.index(string.endIndex, offsetBy: -i)
resultString.append(string[index])
}
print(resultString)

Answer 11

let inputstr = "ABCDEFGHIGKLMNPO"
var resultstr = "";
for strchar in inputstr {
resultstr = String(strchar) + resultstr
}
print("Result = ",resultstr)

Answer 12

Swift 5
extension String {
func invertedEntropy() -> String {
var word = [Character]()
for char in self {
word.insert(char, at: 0)
}
return String(word)
}
}
var palindrome = "TENET"
palindrome.invertedEntropy()
// "TENET"

Answer 13

Simple as that!
let str = "Hello, world!"
let reversed = String(str.reversed())
print(reversed)