Verifying an alien dictionary

Array Hash Table String

55.9% acceptance

Feb 25, 2026

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In an alien language, surprisingly, they also use English lowercase letters, but possibly in a different order. The order of the alphabet is some permutation of lowercase letters. Given a sequence of words written in the alien language, and the order of the alphabet, return true if and only if the given words are sorted lexicographically in this alien language.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn is_alien_sorted(words: Vec<String>, order: String) -> bool {
    let mut rank = [0u8; 26];
    for (i, c) in order.bytes().enumerate() { rank[(c - b'a') as usize] = i as u8; }
    for w in words.windows(2) {
      let a: Vec<u8> = w[0].bytes().map(|c| rank[(c - b'a') as usize]).collect();
      let b: Vec<u8> = w[1].bytes().map(|c| rank[(c - b'a') as usize]).collect();
      if a > b { return false; }
    }
    true
  }
}