leetcode Length of Last Word

题目连接

https://leetcode.com/problems/length-of-last-word/  

Length of Last Word

Description

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.

class Solution {
public:
	int lengthOfLastWord(string s) {
		size_t n = s.length();
		size_t lb = 0, ub = n - 1;
		reverse(s.begin(), s.end());
		while (lb < n)  { if (s[lb] == ' ') lb++; else break; }
		while (ub >= 0) { if (s[ub] == ' ') ub--; else break; }
		if (lb == n && ub == -1) return 0;
		int ans = 0;
		for (size_t i = lb; i <= ub; i++) {
			if (s[i] != ' ') ans++;
			else break;
		}
		return ans;
	}
};