Find the lexicographically largest string from the box ii

Two Pointers String

49.4% acceptance

Mar 31, 2026

You are given a string word, and an integer numFriends. Alice is organizing a game for her numFriends friends. There are multiple rounds in the game, where in each round: word is split into numFriends non-empty strings, such that no previous round has had the exact same split. All the split words are put into a box. Find the lexicographically largest string from the box after all the rounds are finished. A string a is lexicographically smaller than a string b if in the first position where a and b differ, string a has a letter that appears earlier in the alphabet than the corresponding letter in b. If the first min(a.length, b.length) characters do not differ, then the shorter string is the lexicographically smaller one.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn answer_string(word: String, num_friends: i32) -> String {
    if num_friends == 1 {
      return word;
    }
    let n = word.len();
    let max_len = n - (num_friends as usize - 1);
    let bytes = word.as_bytes();
    let mut best_start = 0;
    for i in 1..n {
      if bytes[i] > bytes[best_start] {
        best_start = i;
      } else if bytes[i] == bytes[best_start] {
        let len = max_len.min(n - i).min(n - best_start);
        if word[i..i + len] > word[best_start..best_start + len] {
          best_start = i;
        }
      }
    }
    let end = (best_start + max_len).min(n);
    word[best_start..end].to_string()
  }
}