2019.11.3 #程序员笔试必备# LeetCode 从零单刷个人笔记整理(持续更新)
github:https://github.com/ChopinXBP/LeetCode-Babel
数据结构题,应知应会。
Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out) principle and the last position is connected back to the first position to make a circle. It is also called “Ring Buffer”.
One of the benefits of the circular queue is that we can make use of the spaces in front of the queue. In a normal queue, once the queue becomes full, we cannot insert the next element even if there is a space in front of the queue. But using the circular queue, we can use the space to store new values.
设计你的循环队列实现。 循环队列是一种线性数据结构,其操作表现基于 FIFO(先进先出)原则并且队尾被连接在队首之后以形成一个循环。它也被称为“环形缓冲器”。
循环队列的一个好处是我们可以利用这个队列之前用过的空间。在一个普通队列里,一旦一个队列满了,我们就不能插入下一个元素,即使在队列前面仍有空间。但是使用循环队列,我们能使用这些空间去存储新的值。
你的实现应该支持如下操作:
MyCircularQueue(k): 构造器,设置队列长度为 k 。
Front(): 从队首获取元素。如果队列为空,返回 -1 。
Rear(): 获取队尾元素。如果队列为空,返回 -1 。
enQueue(value): 向循环队列插入一个元素。如果成功插入则返回真。
deQueue(): 从循环队列中删除一个元素。如果成功删除则返回真。
isEmpty(): 检查循环队列是否为空。
isFull(): 检查循环队列是否已满。
示例:
MyCircularQueue circularQueue = new MycircularQueue(3); // 设置长度为 3
circularQueue.enQueue(1); // 返回 true
circularQueue.enQueue(2); // 返回 true
circularQueue.enQueue(3); // 返回 true
circularQueue.enQueue(4); // 返回 false,队列已满
circularQueue.Rear(); // 返回 3
circularQueue.isFull(); // 返回 true
circularQueue.deQueue(); // 返回 true
circularQueue.enQueue(4); // 返回 true
circularQueue.Rear(); // 返回 4
提示:
所有的值都在 0 至 1000 的范围内;
操作数将在 1 至 1000 的范围内;
请不要使用内置的队列库。
import java.util.LinkedList;
/**
*
* Design your implementation of the circular queue. The circular queue is a linear data structure in which the operations are performed based on FIFO (First In First Out)
* principle and the last position is connected back to the first position to make a circle. It is also called "Ring Buffer".
* 设计你的循环队列实现。 循环队列是一种线性数据结构,其操作表现基于 FIFO(先进先出)原则并且队尾被连接在队首之后以形成一个循环。它也被称为“环形缓冲器”。
*
*/
public class DesignCircularQueue {
class MyCircularQueue {
final int[] array;
int head = 0;
int tail = -1;
int size = 0;
/** Initialize your data structure here. Set the size of the queue to be k. */
public MyCircularQueue(int k) {
array = new int[k];
}
/** Insert an element into the circular queue. Return true if the operation is successful. */
public boolean enQueue(int value) {
if(isFull()){
return false;
}
tail = (tail + 1) % array.length;
array[tail] = value;
size++;
return true;
}
/** Delete an element from the circular queue. Return true if the operation is successful. */
public boolean deQueue() {
if(isEmpty()){
return false;
}
head = (head + 1) % array.length;
size--;
return true;
}
/** Get the front item from the queue. */
public int Front() {
return isEmpty() ? -1 : array[head];
}
/** Get the last item from the queue. */
public int Rear() {
return isEmpty() ? -1 : array[tail];
}
/** Checks whether the circular queue is empty or not. */
public boolean isEmpty() {
return size == 0;
}
/** Checks whether the circular queue is full or not. */
public boolean isFull() {
return size == array.length;
}
}
/**
* Your MyCircularQueue object will be instantiated and called as such:
* MyCircularQueue obj = new MyCircularQueue(k);
* boolean param_1 = obj.enQueue(value);
* boolean param_2 = obj.deQueue();
* int param_3 = obj.Front();
* int param_4 = obj.Rear();
* boolean param_5 = obj.isEmpty();
* boolean param_6 = obj.isFull();
*/
}
#Coding一小时,Copying一秒钟。留个言点个赞呗,谢谢你#