leetcode 58 Length of Last Word ----- java

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.

这道题就是给定一个字符串，然后判断最后一个单词的长度。似乎是可以直接调用split()的。。。当然，并不是最优的。但却是最简单的，不过了解一下split()也好

public class Solution {
    public int lengthOfLastWord(String s) {
        String[] tt;
        tt = s.split(" ");
        return tt.length == 0?0:tt[tt.length-1].length();
    }
}

换用正经的做法。也很简单，一次循环搞定。然而是我太天真了，从前向后必然不是最优。。。。

public class Solution {
    public int lengthOfLastWord(String s) {
        int result = 0,len = s.length();
        for( int i = 0;i<len;i++){
            if( s.charAt(i) == ‘ ‘){
                while( i<s.length() && s.charAt(i) == ‘ ‘)
                    i++;
                if( i!= len)
                    result = 1;
            }
            else
                result++;
        }
        return result;
    }
}

好吧，从后往前，这样就ok了。

public class Solution {
    public int lengthOfLastWord(String s) {
        int result = 0,i = s.length()-1;
        while( i>=0 && s.charAt(i) == ‘ ‘ ){
            i--;
        }
        while( i>=0 && s.charAt(i) != ‘ ‘){
            result++;
            i--;
        }
        return result;
    }
}