4.0 KiB
4.0 KiB
id | title | challengeType |
---|---|---|
587d825a367417b2b2512c88 | Reverse a Doubly Linked List | 1 |
Description
Instructions
Tests
tests:
- text: The DoublyLinkedList data structure exists.
testString: assert((function() { var test = false; if (typeof DoublyLinkedList !== 'undefined') { test = new DoublyLinkedList() }; return (typeof test == 'object')})(), 'The DoublyLinkedList data structure exists.');
- text: The DoublyLinkedList has a method called add.
testString: assert((function() { var test = false; if (typeof DoublyLinkedList !== 'undefined') { test = new DoublyLinkedList() }; if (test.add == undefined) { return false; }; return (typeof test.add == 'function')})(), 'The DoublyLinkedList has a method called add.');
- text: The DoublyLinkedList has a method called reverse.
testString: assert((function() { var test = false; if (typeof DoublyLinkedList !== 'undefined') { test = new DoublyLinkedList() }; if (test.reverse == undefined) { return false; }; return (typeof test.reverse == 'function')})(), 'The DoublyLinkedList has a method called reverse.');
- text: Reversing an empty list returns null.
testString: assert((function() { var test = false; if (typeof DoublyLinkedList !== 'undefined') { test = new DoublyLinkedList() }; return (test.reverse() == null); })(), 'Reversing an empty list returns null.');
- text: The reverse method reverses the list.
testString: assert((function() { var test = false; if (typeof DoublyLinkedList !== 'undefined') { test = new DoublyLinkedList() }; test.add(58); test.add(61); test.add(32); test.reverse(); return (test.print().join('') == '326158'); })(), 'The reverse method reverses the list.');
- text: The next and previous references are correctly maintained when a list is reversed.
testString: assert((function() { var test = false; if (typeof DoublyLinkedList !== 'undefined') { test = new DoublyLinkedList() }; test.add(11); test.add(22); test.add(33); test.reverse(); return (test.printReverse().join('') == '112233'); })(), 'The next and previous references are correctly maintained when a list is reversed.');
Challenge Seed
var Node = function(data, prev) {
this.data = data;
this.prev = prev;
this.next = null;
};
var DoublyLinkedList = function() {
this.head = null;
this.tail = null;
// change code below this line
// change code above this line
};
After Test
DoublyLinkedList.prototype = {
add(data) {
if (this.head == null) {
this.head = new Node(data, null);
this.tail = this.head;
} else {
var node = this.head;
var prev = null;
while (node.next != null) {
prev = node;
node = node.next;
};
var newNode = new Node(data, node);
node.next = newNode;
this.tail = newNode;
};
},
print() {
if (this.head == null) {
return null;
} else {
var result = new Array();
var node = this.head;
while (node.next != null) {
result.push(node.data);
node = node.next;
};
result.push(node.data);
return result;
};
},
printReverse() {
if (this.tail == null) {
return null;
} else {
var result = new Array();
var node = this.tail;
while (node.prev != null) {
result.push(node.data);
node = node.prev;
};
result.push(node.data);
return result;
};
}
};
Solution
// solution required