LeetCode 520. Detect Capital

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题目：
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.

思路：
思路其实就是如果长度为1,直接返回true；如果长度大于1,分了四种情况，具体见代码注释。

代码：

class Solution {
public:bool detectCapitalUse(string word) {int len=word.length();//计算word的长度if(len==1){//如果长度为1,直接返回truereturn true;}for(int i=1;i<len;++i){//长度大于1的情况if(isupper(word[0])&&isupper(word[1])){//如果第一位和第二位都为大写if(isupper(word[i])){//如果i位是大写，继续循环continue;}else{//否则直接返回falsereturn false;}}if(isupper(word[0])&&islower(word[1])){//如果第一位为大写而第二五公里为小写if(islower(word[i])){//如果从i位开始一直是小写，继续循环 continue;}else{//否则返回falsereturn false;}}if(islower(word[0])&&islower(word[1])){//如果第一位和第二位都为小写if(islower(word[i])){//如果从i位开始一直是小写，继续循环continue;}else{//否则返回falsereturn false;}}if(islower(word[0])&&isupper(word[1])){//如果第一位为小写而第二位为大写return false;//直接返回false}}return true;//如果循环结束没返回false，那一定符合要求}
};