LeetCode 520: Detect Capital Solution

Master LeetCode problem 520 (Detect Capital), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

520. Detect Capital

Easy

String

Problem Explanation

Explanation

To solve this problem, we need to check if the usage of capitals in the given word is right according to the defined rules. We can achieve this by checking the following conditions:

If all letters are capitals.
If all letters are lowercase.
If only the first letter is capital.

We can iterate through the characters of the word and count the number of uppercase characters and the position of the first uppercase character. Based on these counts, we can determine if the capital usage is right.

Time complexity: O(n) where n is the length of the input word.
Space complexity: O(1)

Solution Code

class Solution {
    public boolean detectCapitalUse(String word) {
        int n = word.length();
        int upperCount = 0;
        int firstUpperIndex = -1;
        
        for (int i = 0; i < n; i++) {
            char ch = word.charAt(i);
            if (Character.isUpperCase(ch)) {
                upperCount++;
                if (i == 0) {
                    firstUpperIndex = 0;
                }
            }
        }
        
        if (upperCount == n || upperCount == 0 || (upperCount == 1 && firstUpperIndex == 0)) {
            return true;
        }
        
        return false;
    }
}

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