QuestionA.java

package Q17_05_Letters_and_Numbers;

public class QuestionA {
	public static char[] extractSubarray(char[] array, int start, int end) {
		if (start > end) return null;		
		char[] subarray = new char[end - start + 1];
		for (int i = start; i <= end; i++) {
			subarray[i - start] = array[i];
		}
		return subarray;
	}
	
	public static boolean hasEqualLettersNumbers(char[] array, int start, int end) {
		int counter = 0;
		for (int i = start; i <= end; i++) {
			if (Character.isLetter(array[i])) {
				counter++;
			} else if (Character.isDigit(array[i])) {
				counter--;
			}
		}
		return counter == 0;
	}
	
	public static char[] findLongestSubarray(char[] array) {
		for (int len = array.length; len > 1; len--) {
			for (int i = 0; i <= array.length - len; i++) {
				if (hasEqualLettersNumbers(array, i, i + len - 1)) {
					return extractSubarray(array, i, i + len - 1);
				}
			}
		}	
		return null;	
	}	
	
	public static void main(String[] args) {
		char b = '1';
		char a = 'a';
		char[] array = {a, b, a, b, a, b, b, b, b, b, a, a, a, a, a, b, a, b, a, b, b, a, a, a, a, a, a, a};
		for (int i = 0; i < array.length; i++) {
			System.out.print(array[i] + " ");
		}
		System.out.println();
		char[] max = findLongestSubarray(array);
		System.out.println(max.length);
		for (int i = 0; i < max.length; i++) {
			System.out.print(max[i] + " ");
		}
		System.out.println("\nIs Valid? " + hasEqualLettersNumbers(max, 0, max.length - 1));
	}

}