Implement Queue by Interface
ID: 546; easy
Solution 1 (Java)
interface InterfaceQueue {
void push(int element);
// define an interface for pop method
/* write your code here */
int pop();
// define an interface for top method
/* write your code here */
int top();
}
class Node {
public int val;
public Node prev, next;
public Node(int val) {
this.val = val;
prev = next = null;
}
}
public class MyQueue implements InterfaceQueue {
/* you can declare your private attributes here */
private Node first, last;
public MyQueue() {
first = last = null;
}
// implement the push method
/* write your code here */
@Override
public void push(int val) {
if (last == null) {
last = new Node(val);
first = last;
} else {
Node newNode = new Node(val);
last.next = newNode;
newNode.prev = last;
last = newNode;
}
}
// implement the pop method
/* write your code here */
@Override
public int pop() {
if (first == null)
return -1;
int popVal = first.val;
first = first.next;
if (first == null) {
last = null;
} else {
first.prev = null;
}
return popVal;
}
// implement the top method
/* write your code here */
@Override
public int top() {
if (first == null)
return -1;
return first.val;
}
}
/**
* Your MyQueue object will be instantiated and called as such:
* MyQueue queue = new MyQueue();
* queue.push(123);
* queue.top(); will return 123;
* queue.pop(); will return 123 and pop the first element in the queue
*/
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