need help on the todos! Factorial.java ---------------- public class Factorial { public static int factorialRecursive(int n) { if (n == 1 || n == 0) { return 1; } return n * factorialRecursive(n - 1); } public static int factorialTailRecursive(int n) { return factorialTailRecursive(n, 1); } // TODO: Rewrite factorialRecursive as a tail-call recursive function. To review, that means // the return statement for the recursive case should contain only a function and no // other operations. The accumulator argument for the function is already set up for you. public static int factorialTailRecursive(int n, int accum) { return 0; } }

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LinkedList.java

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public class LinkedList { static class Node { int data; Node next; } Node node; private int size() { int i = 0; Node n = this.node; while (n != null) { i += 1; n = n.next; } return i; } public int[] toArray() { int[] array = new int[this.size()]; int i = 0; Node n = this.node; while (n != null) { array[i] = n.data; i += 1; n = n.next; } return array; } static public LinkedList fromArray(int[] array) { Node n = null; for (int i = array.length - 1; i >= 0; i--) { Node newNode = new Node(); newNode.data = array[i]; newNode.next = n; n = newNode; } LinkedList list = new LinkedList(); list.node = n; return list; } // TODO: Write a recursive function to combine two sorted linked lists into a new // sorted linked list. This is just like the combine function we went over in // class for the merge sort example, except it operates over linked lists instead // of arrays. private static Node combineRecursive(Node first, Node second) { return null; } public LinkedList combineSorted(LinkedList other) { LinkedList ret = new LinkedList(); ret.node = combineRecursive(this.node, other.node); return ret; } } 

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Permutation.java

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import java.util.Arrays; public class Permutation { private static void swap(Object[] array, int a, int b) { Object tmp = array[a]; array[a] = array[b]; array[b] = tmp; } public static void printPermutationsRecursive(Object[] array) { printPermutationsRecursive(array, 0); } private static void printPermutationsRecursive(Object[] array, int i) { if (i == array.length - 1) { System.out.println(Arrays.toString(array)); } else { for (int k = i; k < array.length; k++) { swap(array, i, k); printPermutationsRecursive(array, i + 1); swap(array, i, k); } } } // TODO: Rewrite printPermutationsRecursive into an iterative form using an explicit stack. // This will likely require making an inner class like we did with the merge-sort // example in class. The source code for that example is available on blackboard if // you would like to review it. public static void printPermutationsIterative(Object[] array) { } }