【Leetcode】520. Detect Capital

Description:

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:

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：

首先，可以遍历整个字符串，定义三条判断规则，通过三条判断规则来判定是否符合条件：第一，如果第一个字母小写，后面都是小写则符合条件，否则不符合条件；第二，如果第一个字母大写，这里分两种情况，如果第二个字母为大写，那么其后面的字母都应该是大写才可符合条件；如果第二个字母为小写，后面的字母就应该是小写才符合条件，否则其余的都不符合条件。

判断大小写可以根据ASCII码值来进行，’A’的ASCII码值为97，’a’的ASCII码值为65，不过以’A’为分界即可。

下面是使用C++的实现过程：

class Solution {public:    bool detectCapitalUse(string word) {        if(word[0]>=97){            for(int i=1; i<word.length(); i++){                if(word[i]>=97){                    continue;                }else return false;            }        }else{            if(word[1]>=97){                for(int i=2; i<word.length(); i++){                    if(word[i]>=97){                        continue;                    }else return false;                }            }else{                for(int i=2; i<word.length(); i++){                    if(word[i]<97){                        continue;                    }else return false;                }            }        }        return true;    }};