Check if string is decomposable into value equal substrings

String

51.0% acceptance

Mar 31, 2026

A value-equal string is a string where all characters are the same. For example, "1111" and "33" are value-equal strings. In contrast, "123" is not a value-equal string. Given a digit string s, decompose the string into some number of consecutive value-equal substrings where exactly one substring has a length of 2 and the remaining substrings have a length of 3. Return true if you can decompose s according to the above rules. Otherwise, return false. A substring is a contiguous sequence of characters in a string.

Solution

Rust

Time O(n²)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn is_decomposable(s: String) -> bool {
    let bytes = s.as_bytes();
    let mut i = 0;
    let mut has_two = false;
    while i < bytes.len() {
      let ch = bytes[i];
      let mut j = i;
      while j < bytes.len() && bytes[j] == ch {
        j += 1;
      }
      let len = j - i;
      let rem = len % 3;
      if rem == 1 {
        return false;
      }
      if rem == 2 {
        if has_two {
          return false;
        }
        has_two = true;
      }
      i = j;
    }
    has_two
  }
}