58. Length of Last Word 最后一个单词的长度

题目链接
tag:

• Easy；

question
  Given a string s consisting of some words separated by some number of 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.

提示：

• 1 <= s.length <= 104
• s consists of only English letters and spaces ' '.
• There will be at least one word in s.

思路：
  这道题要求我们求字符串最后一个单词的长度，很简单倒序遍历，遇到空格跳过，直到遇到第一个字母，开始计数，再遇到空格就退出即可，代码如下：

class Solution {
public:
    int lengthOfLastWord(string s) {
        if (s.empty()) return 0;
        if (s.size() == 1) return 1;

        int count = 0;
        bool flag = true;
        // 从后面开始，遇到空格就跳过，知道遇到第一个字母，开始计数，再遇到空格就break
        for (int i = s.size() - 1; i >= 0 ; --i) {
            if (s[i] == ' ') {
                if (!flag)
                    break;
            }
            else {
                ++count;
                flag = false;
            } 
        }
        return count;
    }
};