58. Length of Last Word

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.

For example,
Given s = "Hello World",
return 5.

Solution:

Method 1: use split()

Use split() to remove spaces.

We check if last element is "".

If not, it should be a word. We safely return its length.



Code:

public class Solution {
    public int lengthOfLastWord(String s) {
        if (s == null || s.length() == 0) {
            return 0;
        }
        int end = s.length() - 1;
        int len = 0;
        while (end >= 0 && s.charAt(end) == ' ') {
            end--;
        }
        while (end >= 0 && s.charAt(end) != ' ') {
            end--;
            len++;
        }
        return len;
    }
}

Method 2: Pointer

Use a point from the end of the string and go backward.

Go back till its not a space, or to the start of the word.

From this point, go back till it's a space, or to the start of the word.

The distance between the above two points is the length of the word.



Code:

public class Solution {
    public int lengthOfLastWord(String s) {
        String[] strs = s.split(" ");
        for (int i = strs.length - 1; i >= 0; i--) {
            if (strs[i].equals("")) {
                continue;
            }
            return strs[i].length();
        }
        return 0;
    }
}