50. leetcode 520. Detect Capital

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:

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.

思路：若第一个字母是小写那么全应该是小写；若第一个字母是大写，那么从第二个字母开始要么全是大写，要么全是小写。