Keyboard Row

Given an array of strings words, return the words that can be typed using letters of the alphabet on only one row of American keyboard like the image below.

In the American keyboard:

• the first row consists of the characters "qwertyuiop",

• the second row consists of the characters "asdfghjkl", and

• the third row consists of the characters "zxcvbnm".

LeetCode Problem - 500

class Solution {
    // Method to find words that can be typed using only one row of the keyboard
    public String[] findWords(String[] words) {
        // List to store words that satisfy the condition
        List<String> resultList = new ArrayList<>();
        // Iterating through each word
        for (String str : words) {
            // Checking if the word can be typed using one row of the keyboard
            if (checkRowNumber(str)) {
                // Adding the word to the result list if it satisfies the condition
                resultList.add(str);
            }
        }
        // Converting the result list to an array and returning it
        return resultList.toArray(new String[0]);
    }

    // Method to check if a word can be typed using one row of the keyboard
    public boolean checkRowNumber(String word) {
        // Defining the rows of the keyboard
        String row1 = "qwertyuiop", row2 = "asdfghjkl", row3 = "zxcvbnm";

        // Getting the first character of the word
        char firstAlphabet = word.charAt(0);
        // Converting the first character to lowercase
        String flag = String.valueOf(firstAlphabet).toLowerCase();

        // Variable to store the row of the keyboard that the word belongs to
        String keyBoardRow = "";
        // Determining the row of the keyboard based on the first character
        if (row1.contains(flag)) {
            keyBoardRow = row1;
        } else if (row2.contains(flag)) {
            keyBoardRow = row2;
        } else {
            keyBoardRow = row3;
        }

        // Checking if all characters of the word belong to the same row
        for (int i = 1; i < word.length(); i++) {
            String flag2 = String.valueOf(word.charAt(i)).toLowerCase();
            if (!keyBoardRow.contains(flag2)) {
                return false;
            }
        }
        // Returning true if all characters belong to the same row
        return true;
    }
}