Word pattern

Hash Table String

43.8% acceptance

Jan 12, 2026

7947

1140

Given a pattern and a string s, find if s follows the same pattern. Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in s. Specifically: Each letter in pattern maps to exactly one unique word in s. Each unique word in s maps to exactly one letter in pattern. No two letters map to the same word, and no two words map to the same letter.

Solution

Rust

Time O(n)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn word_pattern(pattern: String, s: String) -> bool {
    use std::collections::HashMap;
    let words: Vec<&str> = s.split_whitespace().collect();
    let pattern_chars: Vec<char> = pattern.chars().collect();
    
    if pattern_chars.len() != words.len() {
      return false;
    }
    
    let mut char_to_word = HashMap::new();
    let mut word_to_char = HashMap::new();
    
    for (ch, word) in pattern_chars.iter().zip(words.iter()) {
      if let Some(&mapped_word) = char_to_word.get(ch) {
        if mapped_word != *word {
          return false;
        }
      } else {
        char_to_word.insert(*ch, *word);
      }
      
      if let Some(&mapped_char) = word_to_char.get(word) {
        if mapped_char != *ch {
          return false;
        }
      } else {
        word_to_char.insert(*word, *ch);
      }
    }
    
    true
  }
}