Detect Capital

• LeetCode: Detect Capital

• Problem:

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 if it has more than one letter, like "Google".
Otherwise, we define that this word doesn't use capitals in a right way.

• Note:

The input will be a non-empty word consisting of uppercase and lowercase latin letters.

• Examples:

Input: "USA"
Output: True

Input: "FlaG"
Output: False

• Analysis:

Three rules are provided by problem description,

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 if it has more than one letter, like "Google".

• Code - Java:

class Solution {
    public boolean detectCapitalUse(String word) {
        if (word.equals(word.toUpperCase())) {
            return true;
        }
        int len = word.length();
        for (int i = 1; i < len; i++) {
            char ch = word.charAt(i);
            if ('A' <= ch  && ch <= 'Z') {
                return false;
            }
        }
        return true;
    }
}

• Code - C++:

class Solution {
public:
    bool detectCapitalUse(string word) {
        int len = word.length();
        for (int i = 0; i < len; i++) {
            if (word[i] != toupper(word[i])) {
                break;
            }
            if (i == len - 1) {
                return true;
            }
        }
        for (int i = 1; i < len; i++) {
            if ('A' <= word[i] && word[i] <= 'Z') {
                return false;
            }
        }
        return true;
    }
};

• Code - Python:

class Solution(object):
    def detectCapitalUse(self, word):
        """
        :type word: str
        :rtype: bool
        """
        if word == word.upper():
            return True
        wLen = len(word)
        for i in range(1, wLen):
            if ord('A') <= ord(word[i]) and ord(word[i]) <= ord('Z'):
                return False
        return True

• Time Complexity: O(N), N is the length of input word
• Space Compexity: O(1)