Design your implementation of the circular double-ended queue (deque).
Your implementation should support following operations:
MyCircularDeque(k): Constructor, set the size of the deque to be k.
insertFront(): Adds an item at the front of Deque. Return true if the operation is successful.
insertLast(): Adds an item at the rear of Deque. Return true if the operation is successful.
deleteFront(): Deletes an item from the front of Deque. Return true if the operation is successful.
deleteLast(): Deletes an item from the rear of Deque. Return true if the operation is successful.
getFront(): Gets the front item from the Deque. If the deque is empty, return -1.
getRear(): Gets the last item from Deque. If the deque is empty, return -1.
isEmpty(): Checks whether Deque is empty or not.
isFull(): Checks whether Deque is full or not.
Example:
MyCircularDeque circularDeque = new MycircularDeque(3); // set the size to be 3
circularDeque.insertLast(1); // return true
circularDeque.insertLast(2); // return true
circularDeque.insertFront(3); // return true
circularDeque.insertFront(4); // return false, the queue is full
circularDeque.getRear(); // return 2
circularDeque.isFull(); // return true
circularDeque.deleteLast(); // return true
circularDeque.insertFront(4); // return true
circularDeque.getFront(); // return 4
Note:
All values will be in the range of [0, 1000].
The number of operations will be in the range of [1, 1000].
Please do not use the built-in Deque library.
622.Design Circular Queue 的拓展。
解法：doubly Linked List
Java:
class MyCircularDeque {
int size;
int k;
DoubleListNode head;
DoubleListNode tail;
/** Initialize your data structure here. Set the size of the deque to be k. */
public MyCircularDeque(int k) {
head = new DoubleListNode(-1);
tail = new DoubleListNode(-1);
head.pre = tail;
tail.next = head;
this.k = k;
this.size = 0;
}
/** Adds an item at the front of Deque. Return true if the operation is successful. */
public boolean insertFront(int value) {
if (size == k)
return false;
DoubleListNode node = new DoubleListNode(value);
node.next = head;
node.pre = head.pre;
head.pre.next = node;
head.pre = node;
size++;
return true;
}
/** Adds an item at the rear of Deque. Return true if the operation is successful. */
public boolean insertLast(int value) {
if (size == k)
return false;
DoubleListNode node = new DoubleListNode(value);
node.next = tail.next;
tail.next.pre = node;
tail.next = node;
node.pre = tail;
size++;
return true;
}
/** Deletes an item from the front of Deque. Return true if the operation is successful. */
public boolean deleteFront() {
if (size == 0)
return false;
head.pre.pre.next = head;
head.pre = head.pre.pre;
size--;
return true;
}
/** Deletes an item from the rear of Deque. Return true if the operation is successful. */
public boolean deleteLast() {
if (size == 0)
return false;
tail.next.next.pre = tail;
tail.next = tail.next.next;
size--;
return true;
}
/** Get the front item from the deque. */
public int getFront() {
return head.pre.val;
}
/** Get the last item from the deque. */
public int getRear() {
return tail.next.val;
}
/** Checks whether the circular deque is empty or not. */
public boolean isEmpty() {
return size == 0;
}
/** Checks whether the circular deque is full or not. */
public boolean isFull() {
return size == k;
}
}
class DoubleListNode {
DoubleListNode pre;
DoubleListNode next;
int val;
public DoubleListNode(int val) {
this.val = val;
}
}
Python:
class Node:
def __init__(self, value):
self.val = value
self.next = self.pre = None class MyCircularDeque: def __init__(self, k):
self.head = self.tail = Node(-1)
self.head.next = self.tail
self.tail.pre = self.head
self.size = k
self.curSize = 0 def add(self, value, preNode):
new = Node(value)
new.pre = preNode
new.next = preNode.next
new.pre.next = new.next.pre = new
self.curSize += 1 def remove(self, preNode):
node = preNode.next
node.pre.next = node.next
node.next.pre = node.pre
self.curSize -= 1 def insertFront(self, value):
if self.curSize < self.size:
self.add(value, self.head)
return True
return False def insertLast(self, value):
if self.curSize < self.size:
self.add(value, self.tail.pre)
return True
return False def deleteFront(self):
if self.curSize:
self.remove(self.head)
return True
return False def deleteLast(self):
if self.curSize:
self.remove(self.tail.pre.pre)
return True
return False def getFront(self):
if self.curSize:
return self.head.next.val
return -1 def getRear(self):
if self.curSize:
return self.tail.pre.val
return -1 def isEmpty(self):
return self.curSize == 0 def isFull(self):
return self.curSize == self.size
C++:
#include <vector>
#include <iostream> using namespace std; class MyCircularDeque {
private:
vector<int> buffer;
int cnt;
int k;
int front;
int rear;
public:
/** Initialize your data structure here. Set the size of the deque to be k. */
MyCircularDeque(int k): buffer(k, 0), cnt(0), k(k), front(k - 1), rear(0) {
} /** Adds an item at the front of Deque. Return true if the operation is successful. */
bool insertFront(int value) {
if (cnt == k) {
return false;
}
buffer[front] = value;
front = (front - 1 + k) % k;
++cnt; return true;
} /** Adds an item at the rear of Deque. Return true if the operation is successful. */
bool insertLast(int value) {
if (cnt == k) {
return false;
}
buffer[rear] = value;
rear = (rear + 1) % k;
++cnt; return true;
} /** Deletes an item from the front of Deque. Return true if the operation is successful. */
bool deleteFront() {
if (cnt == 0) {
return false;
}
front = (front + 1) % k;
--cnt; return true;
} /** Deletes an item from the rear of Deque. Return true if the operation is successful. */
bool deleteLast() {
if (cnt == 0) {
return false;
}
rear = (rear - 1 + k) % k;
--cnt; return true;
} /** Get the front item from the deque. */
int getFront() {
if (cnt == 0) {
return -1;
}
return buffer[(front + 1) % k];
} /** Get the last item from the deque. */
int getRear() {
if (cnt == 0) {
return -1;
}
return buffer[(rear - 1 + k) % k];
} /** Checks whether the circular deque is empty or not. */
bool isEmpty() {
return cnt == 0;
} /** Checks whether the circular deque is full or not. */
bool isFull() {
return cnt == k;
}
}; /**
* Your MyCircularDeque object will be instantiated and called as such:
* MyCircularDeque obj = new MyCircularDeque(k);
* bool param_1 = obj.insertFront(value);
* bool param_2 = obj.insertLast(value);
* bool param_3 = obj.deleteFront();
* bool param_4 = obj.deleteLast();
* int param_5 = obj.getFront();
* int param_6 = obj.getRear();
* bool param_7 = obj.isEmpty();
* bool param_8 = obj.isFull();
*/ #if DEBUG
int main(int argc, char** argv) {
return 0;
}
#endif
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