LeetCode Entry

387. First Unique Character in a String

05.02.2024 easy 2024 kotlin rust

First non-repeating char position.

387. First Unique Character in a String easy blog post substack youtube image.png

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Problem TLDR

First non-repeating char position.

Intuition

Compute char’s frequencies, then find first of 1.

Approach

Let’s try to make code shorter: Kotlin:

  • groupBy
  • run
  • indexOfFirst Rust:
  • vec![]
  • String.find
  • map_or

Complexity

  • Time complexity: \(O(n)\)

  • Space complexity: \(O(1)\)

Code


  fun firstUniqChar(s: String) = s.groupBy { it }
    .run { s.indexOfFirst { this[it]!!.size < 2 } }



  pub fn first_uniq_char(s: String) -> i32 {
    let mut f = vec![0; 128];
    for b in s.bytes() { f[b as usize] += 1 }
    s.find(|c| f[c as usize] < 2).map_or(-1, |i| i as i32)
  }