Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Chapter 3 | Stacks and Queues
How to Approach:
Whether you are asked to implement a simple stack / queue, or you are asked to implement
a modified version of one, you will have a big leg up on other candidates if you can flawlessly
work with stacks and queues. Practice makes perfect! Here is some skeleton code for a Stack
and Queue class.
Implementing a Stack
1 class Stack {
2 Node top;
3 Node pop() {
4 if (top != null) {
5 Object item = top.data;
6 top = top.next;
7 return item;
8 }
9 return null;
10 }
11 void push(Object item) {
12 Node t = new Node(item);
13 t.next = top;
14 top = t;
15 }
16 }
Implementing a Queue
1 class Queue {
2 Node first, last;
3 void enqueue(Object item) {
4 if (!first) {
5 back = new Node(item);
6 first = back;
7 } else {
8 back.next = new Node(item);
9 back = back.next;
10 }
11 }
12 Node dequeue(Node n) {
13 if (front != null) {
14 Object item = front.data;
15 front = front.next;
16 return item;
17 }
18 return null;
19 }
20 }
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Cracking the Coding Interview | Data Structures