【Java数据结构】实现栈和队列

1. public class MyStack {
2. //栈的底层我们用数组存储数据
3. int[] elements;
4. 
5. public MyStack() {
6.         elements = new int[0];
7.     }
8. //压入元素
9. public void push(int element){
10. //创建一个新数组
11. int[] newArr = new int[elements.length + 1];
12. //把原数组的值复制到新数组中
13. for (int i = 0; i < elements.length; i++) {
14.             newArr[i] = elements[i];
15.         }
16. //把添加的元素放入新数组中
17.         newArr[elements.length] = element;
18. //使用新数组替换旧数组
19.         elements = newArr;
20.     }
21. //取出栈顶元素
22. public int pop(){
23. if (elements.length ==0){
24. throw new RuntimeException("stack is Empty");
25.         }
26. //取出数组中最后一个元素
27. int element = elements[elements.length-1];
28. //创建一个新数组
29. int[] newArr = new int[elements.length-1];
30. for (int i = 0; i < elements.length-1; i++) {
31.             newArr[i] = elements[i];
32.         }
33.         elements = newArr;
34. return element;
35.     }
36. //查看栈顶元素
37. public int peek(){
38. return elements[elements.length-1];
39.     }
40. //判断栈顶是否为空
41. public boolean isEmpty(){
42. return elements.length == 0;
43.     }
44. }

1. public class Test {
2. public static void main(String[] args) {
3. MyStack ms = new MyStack();
4.         ms.push(3);
5.         ms.push(6);
6.         ms.push(4);
7.         ms.push(45);
8.         System.out.println("栈顶元素是"+ms.peek());
9.         ms.pop();
10.         System.out.println("栈顶元素是"+ms.peek());
11.         System.out.println(ms.isEmpty());
12.     }
13. 
14. }

1. public class MyQueue {
2. int[] elements;
3. public MyQueue() {
4.         elements = new int[0];
5.     }
6. public void add(int element){
7. int[] newArr = new int[elements.length+1];
8. for (int i = 0; i < elements.length; i++) {
9.             newArr[i] = elements[i];
10.         }
11.         newArr[elements.length] = element;
12.         elements = newArr;
13.     }
14. public int poll(){
15. if (elements.length == 0){
16. throw new RuntimeException("queue is Empty");
17.         }
18. int element = elements[0];
19. int[] newArr = new int[elements.length - 1];
20. for (int i = 0; i < elements.length - 1; i++) {
21.             newArr[i] = elements[i+1];
22.         }
23.         elements = newArr;
24. return element;
25.     }
26. public boolean isEmpty(){
27. return elements.length == 0;
28.     }
29. 
30. }

1. public class Test {
2. public static void main(String[] args) {
3. MyQueue mq = new MyQueue();
4.         mq.add(1);
5.         mq.add(4);
6.         mq.add(5);
7.         mq.add(45);
8.         System.out.println(mq.poll());
9.         System.out.println(mq.poll());
10.         System.out.println(mq.poll());
11.         System.out.println(mq.poll());
12.         System.out.println(mq.isEmpty());
13. 
14.     }
15. 
16. 
17. }