Latest time by replacing hidden digits

String Greedy

43.6% acceptance

Feb 25, 2026

403

188

You are given a string time in the form of hh:mm, where some of the digits in the string are hidden (represented by ?). The valid times are those inclusively between 00:00 and 23:59. Return the latest valid time you can get from time by replacing the hidden digits.

Solution

Rust

Time O(1)

Space O(1)

LeetCode

solution.rs

impl Solution {
  pub fn maximum_time(time: String) -> String {
    let mut t: Vec<u8> = time.into_bytes();
    // Position 0: tens of hours
    if t[0] == b'?' {
      t[0] = if t[1] == b'?' || t[1] <= b'3' { b'2' } else { b'1' };
    }
    // Position 1: units of hours
    if t[1] == b'?' {
      t[1] = if t[0] == b'2' { b'3' } else { b'9' };
    }
    // Position 3: tens of minutes
    if t[3] == b'?' { t[3] = b'5'; }
    // Position 4: units of minutes
    if t[4] == b'?' { t[4] = b'9'; }
    String::from_utf8(t).unwrap()
  }
}