520. Detect Capital

Problem Statement

Easy

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.

Example 1:

Input: word = "USA"
Output: true

Example 2:

Input: word = "FlaG"
Output: false

Constraints:

1 <= word.length <= 100
word consists of lowercase and uppercase English letters.

C++ — alternative 1

Source file

class Solution {
public:
    bool detectCapitalUse(string word) {
        auto isCaps = [](char c)->bool{return (c>='A' && c<='Z');};
        if(!isCaps(word[0])){    // case 2 -> leetcode
            for(auto c:word)
                if (isCaps(c))
                    return false;
        }else{
            if(isCaps(word[1])){    // case 1 -> USA
                for(auto c:word)
                    if (!isCaps(c))
                        return false;
            }
            else for(auto c:word.substr(1))   // case 3 -> Google
                if (isCaps(c))
                    return false;
        }
        return true;
    }
};

C++ — alternative 2

Source file

class Solution {
public:
    bool detectCapitalUse(string word) {
        int c=0;
        for (int i=0; i<word.length(); i++){
            if(word[i]>='A' && word[i]<='Z')
                c++;
        }
        if(c==word.length()||c==0)
            return true;
        else if(c==1 && word[0]>='A' && word[0]<='Z')
            return true;
        return false;
    }
};