Maximum number of equal length runs

Hash Table String Counting

84.3% acceptance

Mar 31, 2026

You are given a string s consisting of lowercase English letters. A run in s is a substring of equal letters that cannot be extended further. For example, the runs in "hello" are "h", "e", "ll", and "o". You can select runs that have the same length in s. Return an integer denoting the maximum number of runs you can select in s.

Solution

Rust

Time O(n²)

Space O(n)

LeetCode

solution.rs

impl Solution {
  pub fn max_same_length_runs(s: String) -> i32 {
    let b = s.as_bytes();
    let mut counts = std::collections::HashMap::new();
    let mut i = 0;
    while i < b.len() {
      let c = b[i];
      let mut j = i;
      while j < b.len() && b[j] == c {
        j += 1;
      }
      *counts.entry(j - i).or_insert(0) += 1;
      i = j;
    }
    *counts.values().max().unwrap()
  }
}