题目:
设计实现双端队列。
你的实现需要支持以下操作:
MyCircularDeque(k):构造函数,双端队列的大小为k。
insertFront():将一个元素添加到双端队列头部。 如果操作成功返回 true。
insertLast():将一个元素添加到双端队列尾部。如果操作成功返回 true。
deleteFront():从双端队列头部删除一个元素。 如果操作成功返回 true。
deleteLast():从双端队列尾部删除一个元素。如果操作成功返回 true。
getFront():从双端队列头部获得一个元素。如果双端队列为空,返回 -1。
getRear():获得双端队列的最后一个元素。 如果双端队列为空,返回 -1。
isEmpty():检查双端队列是否为空。
isFull():检查双端队列是否满了。
方法一:数组实现
class MyCircularDeque {
int[]a;
int size=0;
/** Initialize your data structure here. Set the size of the deque to be k. */
public MyCircularDeque(int k) {
a=new int[k];
}
/** Adds an item at the front of Deque. Return true if the operation is successful. */
public boolean insertFront(int value) {
if(this.isFull()){
return false;
}
for(int i=this.size;i>0;i--){
a[i]=a[i-1];
}
a[0]=value;
size++;
return true;
}
/** Adds an item at the rear of Deque. Return true if the operation is successful. */
public boolean insertLast(int value) {
if(this.isFull()){
return false;
}
a[size++]=value;
return true;
}
/** Deletes an item from the front of Deque. Return true if the operation is successful. */
public boolean deleteFront() {
if(this.isEmpty()){
return false;
}
for(int i=1;i<size;i++){
a[i-1]=a[i];
}
size--;
return true;
}
/** Deletes an item from the rear of Deque. Return true if the operation is successful. */
public boolean deleteLast() {
if(this.isEmpty()){
return false;
}
size--;
return true;
}
/** Get the front item from the deque. */
public int getFront() {
if(this.isEmpty()){
return -1;
}
return a[0];
}
/** Get the last item from the deque. */
public int getRear() {
if(this.isEmpty()){
return -1;
}
return a[size-1];
}
/** Checks whether the circular deque is empty or not. */
public boolean isEmpty() {
if(this.size==0){
return true;
}
return false;
}
/** Checks whether the circular deque is full or not. */
public boolean isFull() {
if(a.length==size){
return true;
}
return false;
}
}
方法二:循环数组
public class MyCircularDeque {
private int capacity;
private int[] arr;
private int front;
private int rear;
/**
* Initialize your data structure here. Set the size of the deque to be k.
*/
public MyCircularDeque(int k) {
capacity = k + 1;
arr = new int[capacity];
front = 0;
rear = 0;
}
/**
* Adds an item at the front of Deque. Return true if the operation is successful.
*/
public boolean insertFront(int value) {
if (isFull()) {
return false;
}
front = (front - 1 + capacity) % capacity;
arr[front] = value;
return true;
}
/**
* Adds an item at the rear of Deque. Return true if the operation is successful.
*/
public boolean insertLast(int value) {
if (isFull()) {
return false;
}
arr[rear] = value;
rear = (rear + 1) % capacity;
return true;
}
/**
* Deletes an item from the front of Deque. Return true if the operation is successful.
*/
public boolean deleteFront() {
if (isEmpty()) {
return false;
}
// front 被设计在数组的开头,所以是 +1
front = (front + 1) % capacity;
return true;
}
/**
* Deletes an item from the rear of Deque. Return true if the operation is successful.
*/
public boolean deleteLast() {
if (isEmpty()) {
return false;
}
// rear 被设计在数组的末尾,所以是 -1
rear = (rear - 1 + capacity) % capacity;
return true;
}
/**
* Get the front item from the deque.
*/
public int getFront() {
if (isEmpty()) {
return -1;
}
return arr[front];
}
/**
* Get the last item from the deque.
*/
public int getRear() {
if (isEmpty()) {
return -1;
}
// 当 rear 为 0 时防止数组越界
return arr[(rear - 1 + capacity) % capacity];
}
/**
* Checks whether the circular deque is empty or not.
*/
public boolean isEmpty() {
return front == rear;
}
/**
* Checks whether the circular deque is full or not.
*/
public boolean isFull(){
return (rear + 1) % capacity == front;
}
}
来源:CSDN
作者:ZQQ~BK
链接:https://blog.csdn.net/qq_42174669/article/details/103980100