Number of changing keys

String

80.5% acceptance

Feb 25, 2026

163

You are given a 0-indexed string s typed by a user. Changing a key is defined as using a key different from the last used key. For example, s = "ab" has a change of a key while s = "bBBb" does not have any. Return the number of times the user had to change the key. Note: Modifiers like shift or caps lock won't be counted in changing the key that is if a user typed the letter 'a' and then the letter 'A' then it will not be considered as a changing of key.

Solution

Rust

Time O(n)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn count_key_changes(s: String) -> i32 {
    let s: Vec<u8> = s.bytes().map(|b| b.to_ascii_lowercase()).collect();
    s.windows(2).filter(|w| w[0] != w[1]).count() as i32
  }
}