check-in-meeting-answers.md

CSE 143

Check-in Meeting Answers

Week 9

1. hasDuplicates

   public boolean hasDuplicates() {
   	ListNode current = front;
   	while (current != null) {
   		ListNode comparison = current.next;
   		while (comparison != null) {
   			if (comparison.data == current.data) {
   				return true;
   			}
   			else {
   				comparison = comparison.next;
   			}
   		}
   		current = current.next;
   	}
   	return false;
   }

2. addListAt

   public void addListAt(ListNode list, int index) {
   	if (index < 0) {
   		throw newIllegalArgumentException("index negative");
   	}
   	if (list != null) {
   		ListNode oldListAfterIndex = front;
   		ListNode oldListBeforeIndex = null;
   		for(int i = 0; i < index; i++) {
   			if (oldListAfterIndex == null) {
   				throw new IllegalArgumentException("index beyond list");
   			}
   			oldListBeforeIndex = oldListAfterIndex;
   			oldListAfterIndex = oldListAfterIndex.next;
   		}
   		ListNode newListLast = list;
   		while (newListLast.next != null) {
   			newListLast = newListLast.next;
   		}
   		if (oldListBeforeIndex == null) {
   			front = list;
   		}
   		else {
   			oldListBeforeIndex.next = list;
   		}
   		newListLast.next = oldListAfterIndex;
   	}
   }

3. countPathsOfLength

   public int countPathsOfLength(int length) {
   	return countPathsOfLength(this.root, length);
   }
   
   private int countPathsOfLength(IntTreeNode current, int length) {
   	if (current == null && length != 0) {
   		return 0;
   	}
   	else if (current == null && length == 0) {
   		return 1;
   	}
   	else {
   		return countPathsOfLength(current.left, length − 1) + 
   				countPathsOfLength(current.right, length − 1);
   	}
   }