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
理解题意：当字符满足1.全是大写字母
2.全是小写字母
3.首字母大写 则为true否则为false

class Solution {public:    bool detectCapitalUse(string word) {    int len=word.length();    for(int i=0;i<len;i++)    {        if(word[0]<='z'&&word[0]>='a')//首字母是小写        {          if(word[i]>'z'||word[i]<'a')//出现大写则为false               return false;        }        else if(word[0]<='Z'&&word[0]>='A')//首字母大写        {            if(len>=2&&word[1]<='Z'&&word[1]>='A')//次字母大写            {                if(i>1&&i<len&&(word[i]>'Z'||word[i]<'A'))//注意或的符号                    return false;            }            else if(len>=2&&word[1]<='z'&&word[1]>='a')               if(i>1&&i<len&&(word[i]>'z'||word[i]<'a'))                   return false;        }    }    return true;    }};