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This approach involves using a fixed-size array to represent the deque. We'll maintain two indices, front
and rear
, to manage the current front and last positions in the deque. Operations like insertions and deletions are performed by adjusting these indices while ensuring they wrap around using the modulo operation as necessary to remain within the array bounds.
Time Complexity: O(1) for each operation.
Space Complexity: O(k), where k is the capacity of the deque.
1#include <stdbool.h>
2
3typedef struct {
4 int* data;
5 int front;
6 int rear;
7 int size;
8 int capacity;
9} MyCircularDeque;
10
11MyCircularDeque* myCircularDequeCreate(int k) {
12 MyCircularDeque* obj = (MyCircularDeque*) malloc(sizeof(MyCircularDeque));
13 obj->data = (int*) malloc(sizeof(int) * k);
14 obj->front = 0;
15 obj->rear = 0;
16 obj->size = 0;
17 obj->capacity = k;
18 return obj;
19}
20
21bool myCircularDequeInsertFront(MyCircularDeque* obj, int value) {
22 if (obj->size == obj->capacity) return false;
23 obj->front = (obj->front - 1 + obj->capacity) % obj->capacity;
24 obj->data[obj->front] = value;
25 obj->size++;
26 return true;
27}
28
29bool myCircularDequeInsertLast(MyCircularDeque* obj, int value) {
30 if (obj->size == obj->capacity) return false;
31 obj->data[obj->rear] = value;
32 obj->rear = (obj->rear + 1) % obj->capacity;
33 obj->size++;
34 return true;
35}
36
37bool myCircularDequeDeleteFront(MyCircularDeque* obj) {
38 if (obj->size == 0) return false;
39 obj->front = (obj->front + 1) % obj->capacity;
40 obj->size--;
41 return true;
42}
43
44bool myCircularDequeDeleteLast(MyCircularDeque* obj) {
45 if (obj->size == 0) return false;
46 obj->rear = (obj->rear - 1 + obj->capacity) % obj->capacity;
47 obj->size--;
48 return true;
49}
50
51int myCircularDequeGetFront(MyCircularDeque* obj) {
52 if (obj->size == 0) return -1;
53 return obj->data[obj->front];
54}
55
56int myCircularDequeGetRear(MyCircularDeque* obj) {
57 if (obj->size == 0) return -1;
58 return obj->data[(obj->rear - 1 + obj->capacity) % obj->capacity];
59}
60
61bool myCircularDequeIsEmpty(MyCircularDeque* obj) {
62 return obj->size == 0;
63}
64
65bool myCircularDequeIsFull(MyCircularDeque* obj) {
66 return obj->size == obj->capacity;
67}
68
69void myCircularDequeFree(MyCircularDeque* obj) {
70 free(obj->data);
71 free(obj);
72}
This implementation uses a circular array to manage the deque operations. The array is of fixed size, calculated by the given capacity, and follows the circular method to use the front
and rear
indices effectively. The modulo operation is crucial to wrap around these indices and prevent them from exceeding array bounds.
This approach makes use of a doubly linked list to implement the deque. This is particularly effective because it offers dynamic memory usage which can grow or shrink with the number of elements, instead of relying on a pre-allocated fixed-size structure as with arrays.
Time Complexity: O(1) for all operations.
Space Complexity: O(n), where n is the number of elements currently in the deque (potentially more efficient if n is much less than the initial capacity).
1 public int Value;
public Node Next;
public Node Prev;
public Node(int value) {
Value = value;
Next = Prev = null;
}
}
public class MyCircularDeque {
private Node front;
private Node rear;
private int size;
private int capacity;
public MyCircularDeque(int k) {
front = rear = null;
size = 0;
capacity = k;
}
public bool InsertFront(int value) {
if (IsFull()) return false;
Node node = new Node(value);
node.Next = front;
if (front != null) front.Prev = node;
front = node;
if (rear == null) rear = node;
size++;
return true;
}
public bool InsertLast(int value) {
if (IsFull()) return false;
Node node = new Node(value);
node.Prev = rear;
if (rear != null) rear.Next = node;
rear = node;
if (front == null) front = node;
size++;
return true;
}
public bool DeleteFront() {
if (IsEmpty()) return false;
front = front.Next;
if (front != null) front.Prev = null;
else rear = null;
size--;
return true;
}
public bool DeleteLast() {
if (IsEmpty()) return false;
rear = rear.Prev;
if (rear != null) rear.Next = null;
else front = null;
size--;
return true;
}
public int GetFront() {
return IsEmpty() ? -1 : front.Value;
}
public int GetRear() {
return IsEmpty() ? -1 : rear.Value;
}
public bool IsEmpty() {
return size == 0;
}
public bool IsFull() {
return size == capacity;
}
}
In C#, the linked list model for the deque supports dynamic sizing, letting each node connect bidirectionally, which allows rapid pointer modifications for diverse operations at both front and end.