Making file names unique

Array Hash Table String

38.4% acceptance

Feb 25, 2026

464

741

Given an array of strings names of size n. You will create n folders in your file system such that, at the ith minute, you will create a folder with the name names[i]. Since two files cannot have the same name, if you enter a folder name that was previously used, the system will have a suffix addition to its name in the form of (k), where, k is the smallest positive integer such that the obtained name remains unique. Return an array of strings of length n where ans[i] is the actual name the system will assign to the ith folder when you create it.

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

use std::collections::HashMap;

impl Solution {
  pub fn get_folder_names(names: Vec<String>) -> Vec<String> {
    let mut used: HashMap<String, u32> = HashMap::new();
    let mut result = Vec::with_capacity(names.len());
    for name in names {
      if !used.contains_key(&name) {
        used.insert(name.clone(), 1);
        result.push(name);
      } else {
        let mut k = *used.get(&name).unwrap();
        loop {
          let candidate = format!("{}({})", name, k);
          k += 1;
          if !used.contains_key(&candidate) {
            *used.get_mut(&name).unwrap() = k;
            used.insert(candidate.clone(), 1);
            result.push(candidate);
            break;
          }
        }
      }
    }
    result
  }
}