LeetCode:Detect Capital（检测大小写字母）

Given a word, you need to judge whether the usage of capitals in it is right or not.

We define the usage of capitals in a word to be right when one of the following cases holds:

1. All letters in this word are capitals, like "USA".
2. All letters in this word are not capitals, like "leetcode".
3. Only the first letter in this word is capital if it has more than one letter, like "Google".

Otherwise, we define that this word doesn't use capitals in a right way.

Example 1:

---

Input: "USA"
Output: True

---

Example 2:

---

Input: "FlaG"
Output: False

---

Note: The input will be a non-empty word consisting of uppercase and lowercase latin letters.

class Solution {
    public boolean detectCapitalUse(String word) {
        if (word.length() <= 1) {
            return true;
        }
        boolean firstCharFlag = word.charAt(0) < 97;
        boolean secondCharFlag = word.charAt(1) < 97;
       
        if (!firstCharFlag && secondCharFlag) {
            return false;
        }
        
        for (int i = 2; i < word.length(); i++) {
            boolean charFlag = word.charAt(i) < 97;
            //存在第二个字符和后面的字符不相同返回都为false
            if (!secondCharFlag && charFlag) {
                return false;
            }
            if (secondCharFlag && !charFlag) {
                return false;
            }
        }
        return true;       
    }
}

这种方法判断比较简单，而且时间复杂度可以接受，也达到了题目的要求；

很明显这个题目时间复杂度为：0（n）。