How to swap two char in String in Rust

Question

I am trying swap two chars in a String. Here is My Code, I guess there must be a better way to do this.

pub fn swap(s: &String, from_idx: usize, to_idx: usize) -> String { let a = s.clone().chars().nth(from_idx).unwrap(); let b = s.clone().chars().nth(to_idx).unwrap(); let mut result = s.clone(); result.replace_range(from_idx..from_idx + 1, &b.to_string()); result.replace_range(to_idx..to_idx + 1, &a.to_string()); return result; }

Is there a better way, such as shorter syntax or better perfomance?

Although not a duplicate, you might also find more information at this answer — Filipe Rodrigues
– Filipe Rodrigues, Commented Dec 8, 2021 at 13:06
“Is there a better way” Yes. Swapping Unicode Scalar Values makes little to no sense. You probably shouldn't be using a string in the first place. — mcarton
– mcarton, Commented Dec 8, 2021 at 14:31
Note also that the code in question is swapping bytes, not chars. So it will panic if characters on the provided indices are not ASCII - play.rust-lang.org/…. — Cerberus
– Cerberus, Commented Dec 8, 2021 at 15:55

Akida · Accepted Answer · 2021-12-08 13:03:55Z

3

My approach would be:

pub fn swap(s: &str, from_idx: usize, to_idx: usize) -> String { // create a Vec of all characters let mut chars: Vec<_> = s.chars().collect(); // swap the characters in the Vec chars.swap(from_idx, to_idx); // convert Vec back to String chars.into_iter().collect() }

edited Dec 8, 2021 at 13:03

answered Dec 8, 2021 at 12:52

Akida

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6 Comments

En Xie Over a year ago

thank you, Now I know Vec has the swap method can do the trick

Filipe Rodrigues Over a year ago

Also see Why is it discouraged to accept a reference to a String (&String), Vec (&Vec), or Box (&Box) as a function argument?

mcarton Over a year ago

This will seem to work on simple strings with simple Unicode, but not in general. Swapping Unicode Scalar Value makes no sense. There's almost no correct use for str::chars.

Jmb Over a year ago

@hackape swapping characters 0 and 2 in this string: èa (yes it contains three characters) will give àe (probably not what you expect)

Jmb Over a year ago

Here's a playground that illustrates my previous comment.

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