58. Length of Last Word

Description of the Problem

Given a string s consisting of words and spaces, return the length of the last word in the string.

A word is a maximal substring consisting of non-space characters only.

Example 1:

Input: s = "Hello World"
Output: 5
Explanation: The last word is "World" with length 5.

Example 2:

Input: s = "   fly me   to   the moon  "
Output: 4
Explanation: The last word is "moon" with length 4.

Example 3:

Input: s = "luffy is still joyboy"
Output: 6
Explanation: The last word is "joyboy" with length 6.

Constraints:

• 1 <= s.length <= 10^4
• s consists of only English letters and spaces ' '. There will be at least one word in s.

Solution

Code (Rust)

impl Solution {
    pub fn length_of_last_word(s: String) -> i32 {
        let mut count = 0;
        for c in s.chars().rev() {
            match (c==' ', count == 0) {
                (false, _) => count += 1,
                (true, false) => return count,
                (true, true) => {}
            }
        }
        return count;
    }
}

Complexity

• n the length of string s

Time Complexity:

• \(T(n) = O(n)\)

Auxiliary Space:

• \(T(n) = O(1)\)