Length of Last Word¶

Description¶

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.

Test Cases

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.

Approach 1: Using double loop¶

Time Complexity: O(n)
Space Complexity: O(1)

function lengthOfLastWord(s: string): number {
  let count = 0;
  let i = s.length - 1;

  while (i > 0 && s[i] === " ") {
    i--;
  }

  while (i > 0 && s[i] !== " ") {
    count++;
    i--;
  }
  return count;
}
console.log(lengthOfLastWord("Hello World")); // 5

Approach 2: Using single loop¶

Time Complexity: O(n)
Space Complexity: O(1)

function lengthOfLastWord(s: string): number {
  let count = 0;
  let i = s.length - 1;
  while (i >= 0) {
    if (s[i] !== " ") {
      count++;
    } else if (count > 0) {
      break;
    }
    i--;
  }
  return count;
}
console.log(lengthOfLastWord("Hello World")); // 5