58.Length of Last Word

Description

	#58	Length of Last Word	Easy
		String	Top 150
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.

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.

Two-pointers

Runtime 0ms		Memory 41.34MB

class Solution {
    public int lengthOfLastWord(String s) {
        int right = s.length() -1;
        while(s.charAt(right) == ' ' && right > 0) {
            right --;
        }
        int left = right;
        while(left >= 0 && s.charAt(left) != ' ') {
            left --;
        }
        return right - left;
    }
}

State machine

Runtime 0ms		Memory 41.26MB

class Solution {
    enum State {
        EMPTY,
        STRING,
        END
    }
    public int lengthOfLastWord(String s) {
        State state = State.EMPTY;
        int length = 0;
        for(int i = s.length() -1; i >= 0; i--) {
            switch(state) {
                case State.EMPTY: {
                    if(s.charAt(i) == ' ') break;
                    else {
                        state = State.STRING;
                        length ++;
                        break;
                    }
                }
                case State.STRING: {
                    if(s.charAt(i) != ' ') {
                        length ++;
                        break;
                    } else {
                        state = State.END;
                        break;
                    }
                }
                case State.END: return length;
                default: break;
            }  
        }
        return length;
    }
}