641. 设计循环双端队列
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算法记录
LeetCode 题目:
设计实现双端队列。
说明
一、题目
实现相关的方法。
二、分析
- 可用双向链表进行求解,也可用循环队列进行存储。
class Node{
Integer value;
Node first;
Node last;
public Node(int val) {
value = val;
first = null;
last = null;
}
}
class MyCircularDeque {
private Integer size;
private Integer count;
private Node front;
private Node rear;
/** Initialize your data structure here. Set the size of the deque to be k. */
public MyCircularDeque(int k) {
size = k;
count = 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;
Node temp = new Node(value);
if(isEmpty()) {
front = rear = temp;;
} else {
temp.last = front;
front.first = temp;
front = front.first;
}
count++;
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;
Node temp = new Node(value);
if(isEmpty()) {
front = rear = temp;
} else {
rear.last = temp;
temp.first = rear;
rear = rear.last;
}
count++;
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 = front.last;
count--;
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 = rear.first;
count--;
return true;
}
/** Get the front item from the deque. */
public int getFront() {
if(isEmpty()) return -1;
return front.value;
}
/** Get the last item from the deque. */
public int getRear() {
if(isEmpty()) return -1;
return rear.value;
}
/** Checks whether the circular deque is empty or not. */
public boolean isEmpty() {
return count == 0;
}
/** Checks whether the circular deque is full or not. */
public boolean isFull() {
return count == size;
}
}
/**
* Your MyCircularDeque object will be instantiated and called as such:
* MyCircularDeque obj = new MyCircularDeque(k);
* boolean param_1 = obj.insertFront(value);
* boolean param_2 = obj.insertLast(value);
* boolean param_3 = obj.deleteFront();
* boolean param_4 = obj.deleteLast();
* int param_5 = obj.getFront();
* int param_6 = obj.getRear();
* boolean param_7 = obj.isEmpty();
* boolean param_8 = obj.isFull();
*/
总结
熟悉队列的存储性质。
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