Word subsets

Array Hash Table String

55.9% acceptance

Feb 25, 2026

3533

316

You are given two string arrays words1 and words2. A string b is a subset of string a if every letter in b occurs in a including multiplicity. For example, "wrr" is a subset of "warrior" but is not a subset of "world". A string a from words1 is universal if for every string b in words2, b is a subset of a. Return an array of all the universal strings in words1. You may return the answer in any order.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn word_subsets(words1: Vec<String>, words2: Vec<String>) -> Vec<String> {
    let freq2 = words2.iter().fold([0u32; 26], |mut acc, w| {
      let mut f = [0u32; 26];
      for b in w.bytes() { f[(b - b'a') as usize] += 1; }
      for i in 0..26 { acc[i] = acc[i].max(f[i]); }
      acc
    });
    words1.into_iter().filter(|w| {
      let mut f = [0u32; 26];
      for b in w.bytes() { f[(b - b'a') as usize] += 1; }
      (0..26).all(|i| f[i] >= freq2[i])
    }).collect()
  }
}