LeetCode 520 Detect Capital

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:

All letters in this word are capitals, like “USA”.
All letters in this word are not capitals, like “leetcode”.
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.
这个题是一个字符串合法性判断的题目，可以考虑用DFA。LeetCode 65（https://leetcode.com/problems/valid-number/#/description）也是类似的题目，不过65题AC率只有12.7%，一度是AC率最低的题。闲言少叙。看这个题。

我划分了7个状态：

0 开始

1 只有一个大写字母

2 只有一个小写字母

3 大写后面加了一个大写

4 大写后面加了一个小写

5 小写后边加了一个小写

6 非法（exit）

状态矩阵：

 0123450(大写)1363661(小写)245655

显而易见地得出代码：

123456789101112131415

public boolean detectCapitalUse(String word) {int[][] matrix = { { 1, 3, 6, 3, 6, 6 }, { 2, 4, 5, 6, 5, 5 } };int status = 0;for (int i = 0; i < word.length(); i++) {char c = word.charAt(i);if (c >= 'a' && c < = 'z') {status = matrix[1][status];} else {status = matrix[0][status];}if (status == 6)return false;}return true;}