How to obtain the length of the last word in the string

Question

I have reversed the string and have a for loop to iterate through the reversed string.

I am counting characters and I know I have a logic flaw, but I cannot pinpoint why I am having this issue.

The solution needs to return the length of the last word in the string.

My first thought was to iterate through the string backward (I don't know why I decided to create a new string, I should have just iterated through it by decrementing my for loop from the end of the string).

But the logic should be the same from that point for my second for loop.

My logic is basically to try to count characters that aren't whitespace in the last word, and then when the count variable has a value, as well as the next whitespace after the count has counted the characters of the last word.

class Solution {
    public int lengthOfLastWord(String s) {
        int count = 0;
        int countWhite = 0;
        char ch;
        String reversed = "";
        for(int i = 0; i < s.length(); i++) {
            ch = s.charAt(i);
            reversed += ch;
        }
        
        for(int i = 0; i < reversed.length(); i++) {
            if(!Character.isWhitespace(reversed.charAt(i))) {
                count++;
                if(count > 1 && Character.isWhitespace(reversed.charAt(i)) == true) {
                    break;
                }
            }
        }
        return count;
        
    }
}

Answer 1

Maybe try this,

public int lengthOfLastWord(String s) {
    
String [] arr = s.trim().split(" ");


return arr[arr.length-1].length();

}

Answer 2

Another option would be to use index of last space and calculate length from it:

public int lengthOfLastWord(String string) {
    int whiteSpaceIndex = string.lastIndexOf(" ");
    if (whiteSpaceIndex == -1) {
        return string.length();
    }
    int lastIndex = string.length() - 1;
    return lastIndex - whiteSpaceIndex;
}

String.lastIndexOf() finds the start index of the last occurence of the specified string. -1 means the string was not found, in which case we have a single word and length of the entire string is what we need. Otherwise means we have index of the last space and we can calculate last word length using lastIndexInWord - lastSpaceIndex.