58. Length of Last Word

Problem

Given a string s consists of upper/lower-case alphabets and empty space characters ' ', return the length of last word in the string.

If the last word does not exist, return 0.

Note: A word is defined as a character sequence consists of non-space characters only.

Example:

Input: "Hello World"
Output: 5

Solution (Java)

class Solution {
    public int lengthOfLastWord(String str) {
        int len = 0;
        for (int i = str.length() - 1; i >= 0; i--) {
            char ch = str.charAt(i);
            if (ch == ' ' && len > 0) {
                break;
            } else if (ch != ' ') {
                len++;
            }
        }
        return len;
    }
}

Solution (Javascript)

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLastWord = function(s) {
  var str = s.trim();
  var len = str.length;
  var i = len - 1;
  while (i >= 0 && str[i] !== ' ') i--;
  return len - 1 - i;
};

Explain:

nope.

Complexity:

• Time complexity : O(n).
• Space complexity : O(1).