Formatted question description: https://leetcode.ca/all/520.html

520. Detect Capital (Easy)

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, 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.

Related Topics:
String

Solution 1.

// OJ: https://leetcode.com/problems/detect-capital/

// Time: O(N)
// Space: O(1)
class Solution {
public:
    bool detectCapitalUse(string word) {
        if (word.size() < 2) return true;
        bool a = isupper(word[0]), b = isupper(word[1]), upper = a && b;
        if (!a && b) return false;
        for (int i = 2; i < word.size(); ++i) {
            if (isupper(word[i]) > 0 != upper) return false;
        }
        return true;
    }
};

Solution 2.

// OJ: https://leetcode.com/problems/detect-capital/

// Time: O(N)
// Space: O(1)
class Solution {
public:
    bool detectCapitalUse(string word) {
        int cnt = 0;
        for (char c : word) cnt += isupper(c) > 0;
        return !cnt || cnt == word.size() || cnt == 1 && isupper(word[0]);
    }
};

Java

class Solution {
    public boolean detectCapitalUse(String word) {
        if (word == null)
            return false;
        int length = word.length();
        if (length <= 1)
            return true;
        char c0 = word.charAt(0);
        boolean firstCapital = isCapital(c0);
        if (firstCapital) {
            char prevC = word.charAt(1);
            for (int i = 2; i < length; i++) {
                char curC = word.charAt(i);
                if (isCapital(prevC) ^ isCapital(curC))
                    return false;
                prevC = curC;
            }
            return true;
        } else {
            for (int i = 1; i < length; i++) {
                char c = word.charAt(i);
                if (isCapital(c))
                    return false;
            }
            return true;
        }
    }

    public boolean isCapital(char c) {
        return c >= 'A' && c <= 'Z';
    }
}

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