Reverse Strings without using predefined functions - swift

Question

Pardon me as I am a newbie on this language.
Edit: Is there a way to reverse the position of a array element?
I am trying to create a function that test the given input if its a palindrome or not. I'm trying to avoid using functions using reversed()
let word = ["T","E","S","T"]
var temp = [String]()
let index_count = 3
for words in word{
var text:String = words
print(text)
temp.insert(text, atIndex:index_count)
index_count = index_count - 1
}

Answer 1

Your approach can be used to reverse an array. But you have to
insert each element of the original array at the start position
of the destination array (moving the other elements to the end):
// Swift 2.2:
let word = ["T", "E", "S", "T"]
var reversed = [String]()
for char in word {
reversed.insert(char, atIndex: 0)
}
print(reversed) // ["T", "S", "E", "T"]
// Swift 3:
let word = ["T", "E", "S", "T"]
var reversed = [String]()
for char in word {
reversed.insert(char, at: 0)
}
print(reversed) // ["T", "S", "E", "T"]
The same can be done on the characters of a string directly:
// Swift 2.2:
let word = "TEST"
var reversed = ""
for char in word.characters {
reversed.insert(char, atIndex: reversed.startIndex)
}
print(reversed) // "TSET"
// Swift 3:
let word = "TEST"
var reversed = ""
for char in word.characters {
reversed.insert(char, at: reversed.startIndex)
}
print(reversed)

Answer 2

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

Answer 3

Here's my solution:
extension String {
func customReverse() -> String {
var chars = Array(self)
let count = chars.count
for i in 0 ..< count/2 {
chars.swapAt(i, count - 1 - i)
}
return String(chars)
}
}
let input = "abcdef"
let output = input.customReverse()
print(output)
You can try it here.

Answer 4

func reverse(_ str: String) -> String {
let arr = Array(str) // turn the string into an array of all of the letters
let reversed = ""
for char in arr {
reversed.insert(char, at: reversed.startIndex)
}
return reversed
}
To use it:
let word = "hola"
let wordReversed = reverse(word)
print(wordReversed) // prints aloh

Answer 5

Another solution for reversing:
var original : String = "Test"
var reversed : String = ""
var c = original.characters
for _ in 0..<c.count{
reversed.append(c.popLast()!)
}
It simply appends each element of the old string that is popped, starting at the last element and working towards the first

Answer 6

Solution 1
let word = "aabbaa"
let chars = word.characters
let half = chars.count / 2
let leftSide = Array(chars)[0..<half]
let rightSide = Array(chars.reverse())[0..<half]
let palindrome = leftSide == rightSide
Solution 2
var palindrome = true
let chars = Array(word.characters)
for i in 0 ..< (chars.count / 2) {
if chars[i] != chars[chars.count - 1 - i] {
palindrome = false
break
}
}
print(palindrome)

Answer 7

static func reverseString(str : String) {
var data = Array(str)
var i = 0// initial
var j = data.count // final
//either j or i for while , data.count/2 buz only half we need check
while j != data.count/2 {
print("befor i:\(i) j:\(j)" )
j = j-1
data.swapAt(i, j) // swapAt API avalible only for array in swift
i = i+1
}
print(String(data))
}

Answer 8

//Reverse String
let str = "Hello World"
var reverseStr = ""
for char in Array(str) {
print(char)
reverseStr.insert(char, at: str.startIndex)
}
print(reverseStr)