Leetcode: 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.

bool ischar(char p)
	{
		return ('a'<=p && p<='z')||('A'<=p && p<='Z');
	}
	int lengthOfLastWord(const char *s) {
        // Note: The Solution object is instantiated only once.
		int len = strlen(s);
		if(len<1)return 0;

		int end = len-1;
		while((end>=0)&&(s[end] == ' '))end--;

		int begin = end;
		while((begin>=0)&& ischar(s[begin]))begin--;

		return end-begin;		
    }