class SwapAndMergeOnlineTestProblem {
    public static void main(String[] args) {
		int a[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 };
 
		int res[]=mergeArray(a, 3);
		for (int t : res)
			System.out.println(t);
	}
 
	public static int[] mergeArray(int[] inputArray, int totalUnits) {
		int[] outputArray = new int[inputArray.length];
		int unitLength = inputArray.length / totalUnits;
		int k = 0;
		for (int i = 0; i < unitLength; i++) {
			for (int j = 0; j < totalUnits; j++)
				outputArray[k++] = inputArray[i + j * unitLength];
		}
		return outputArray;
	}
 
}
 

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