Length of Last Word LeetCode Solution | Easy Approach

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Length of Last Word | Given a string s consisting of some words separated by some number of spaces, return the length of the last word in the string.

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 <= 104
  • s consists of only English letters and spaces ' '.
  • There will be at least one word in s.

Length of Last Word Solutions

Time: O(n)
Space: O(1)

C++

 class Solution {
 public:
  int lengthOfLastWord(string s) {
    int i = s.length() - 1;

    while (i >= 0 && s[i] == ' ')
      --i;
    const int lastIndex = i;
    while (i >= 0 && s[i] != ' ')
      --i;

    return lastIndex - i;
  }
};

Java

 class Solution {
  public int lengthOfLastWord(String s) {
    int i = s.length() - 1;

    while (i >= 0 && s.charAt(i) == ' ')
      --i;
    final int lastIndex = i;
    while (i >= 0 && s.charAt(i) != ' ')
      --i;

    return lastIndex - i;
  }
}

Python

 class Solution:
  def lengthOfLastWord(self, s: str) -> int:
    i = len(s) - 1

    while i >= 0 and s[i] == ' ':
      i -= 1
    lastIndex = i
    while i >= 0 and s[i] != ' ':
      i -= 1

    return lastIndex - i

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