Java-based nCr on an array for @AlexaCain and @lhsu92 - Gets all `r` combinations on an array of ints

NCR.java

class NCR {

    // Take the factorial of an integer
    public static int factorial(int num)
    {
	int fact = 1;
	for (int i = 1; i <= num; i++)
	    fact = fact*i;
	return fact;
    }

    // Get the nCr
    public static int nCr(int n, int r) {
	return factorial(n)/(factorial(n-r)*factorial(r));
    }

    // Get the combinations of the array
    public static int[][] nCrArray(int[] array, int r) {
	int n = array.length;
	// Choose r from the length of the array
	int ncr = nCr(n,r);
	int[][] result = new int[ncr][r];
	int result_index = 0;
	// BASE CASE
	if (r == 1) {
	    // Each value in the array is a result
	    for (; result_index < array.length; result_index++)
		result[result_index][0] = array[result_index];
	}
	// All other cases
	else {
	    // Iterate through each of the starting values
	    for (int i = 0; i < array.length-r+1; i++) {
		// Create the sub-array
		int[] recursivearray = new int[n-i-1];
		// Copy into the sub-array all values after the active value
		System.arraycopy(array, i+1, recursivearray, 0, n-i-1);
		// Calculate the sub-combinations (recurse)
		int[][] subarrays = nCrArray(recursivearray, r-1);
		// Create the results for this active value
		for (int j = 0; j < subarrays.length; j++) {
		    // Augment the active value and sub-combinations
		    result[result_index][0] = array[i];
		    System.arraycopy(subarrays[j], 0,
				     result[result_index], 1,
				     subarrays[j].length);
		    result_index++;
		}
	    }
	}
	return result;
    }

    public static void main(String[] args) {
	int[] array = {1,2,3,4,5,6,7};
	int r = 4;
	int[][] answer = nCrArray(array, r);
	for (int i = 0; i < answer.length; i++) {
	    for (int j = 0; j < answer[i].length-1; j++) {
		System.out.print(answer[i][j] + ",");
	    }
	    System.out.println(answer[i][answer[i].length-1]);
	}
    }

}