520. Detect Capital

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, like “Google”.

Given a string word, return true if the usage of capitals in it is right.

class Solution {
public:
    bool detectCapitalUse(string word) {
        int up = 0;
        for(auto w : word) if(isupper(w)) up += 1;
        if(up == word.size()) return true;
        if(up == 0) return true;
        if(up == 1 and isupper(word[0])) return true;
        return false;
    }
};