How To Solve This Apple Coding Interview Question With Recursion

Solution to a very popular coding interview question asked recently by Apple.

#softwareengineering #javascript #shorts

[rochie]

Splitting a return statement over 2 lines is a war crime

[AndrewTSq]

The compiler "So what you say you want is a for-loop"

[evanfreethy]

Bonus question. About how large would the string need to be in order for this solution to produce a stack overflow error

[MrAntiKnowledge]

Oh boy the overhead.
Thats a great example for when NOT to use recursion.

[ashiqurrahman-nuik]

Prefer doing it using the first item

def rev(s: str):
if len(s) == 1:
return s[0]

return rev(s[1:]) + s[0]

[malikau]

Dude thanks for these shorts!! I enjoy watching them just as funny food delivery shorts (yes, take this as a compliment)

[qwertioxgame]

I'm c++ programmer and i wonder - why recursion when basic loop would be the same with better memory complexy, even better you can just loop over half of string and just swap chars (also in cpp you can use reverse iterator)

[hajii]

I did:

If (str.length < 2) return str;
return str.charAt(str.length -1) + solution(str.substring(1, str.length -1)) + str.charAt(0)

[romazherdev]

Slicing the string for every character seems like an overkill.

1. Add index to track the current character
2. Start from the last - solution(str, str.length - 1)
3. If i == 0 return str[0]
4. return str[i] + solution(str, i - 1)

[cabbage-dev]

Getting better. I solved this one in my head

[jeffreymarte]

I thought the whole purpose of these coding interviews were to test your algorithms and data structures skills and using slice() would defeat that purpose.

[robertochostakovis]

Recursion is cool, but you have to take care of stack size.

[Cyrrex]

I'd try to do something like

reverse(&text, index1, index2)
If index1 > index2 return ""

Swap(text[index1], text[index2])
Return reverse(text, ++index1, --index2)

This may swap the middle char with itself when the string is of uneven length.

Yeah, but depending on language a simple,

txt = txt[-1:0] could do it without recursion

[nanonkay]

function solution(str) {
if(str.length <= 1) return str
return solution(str.substring(1)) + str.charAt(0)
}

[noobdevtutorials]

function reverseString(string) {
if(string.length === 1) return string
return string.slice(-1) + reverseString(string.slice(0, -1))
}

[asdfghyter]

being a haskeller, recursion is the only way available for reversing a string:

reverse :: String -> String
reverse = go []
where
go acc [] = acc
go acc (x:xs) = go (x:acc) xs

[YT-Gmailer]

arr = str.split("")
while arr.length > 0
revStr += arr.pop()
return revStr

[Lawrence]

at that point you might as well return

[Sensenwerk]

Recursion is illegal in NASA programming.


The reason, it's prone to error/unpredictable outcomes for anything slightly more complex than this.

[JacobChristiansen]

function reverse(str, result = '') {
if (str.length === 0) return result

const [head, ...tail] = str

return reverse(tail, head + result)

}