hello-algo/en/codes/cpp/chapter_stack_and_queue/array_deque.cpp

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/**
* File: array_deque.cpp
* Created Time: 2023-03-02
* Author: krahets (krahets@163.com)
*/
#include "../utils/common.hpp"
/* Double-ended queue class based on circular array */
class ArrayDeque {
private:
vector<int> nums; // Array used to store elements of the double-ended queue
int front; // Front pointer, pointing to the front element
int queSize; // Length of the double-ended queue
public:
/* Constructor */
ArrayDeque(int capacity) {
nums.resize(capacity);
front = queSize = 0;
}
/* Get the capacity of the double-ended queue */
int capacity() {
return nums.size();
}
/* Get the length of the double-ended queue */
int size() {
return queSize;
}
/* Determine if the double-ended queue is empty */
bool isEmpty() {
return queSize == 0;
}
/* Calculate circular array index */
int index(int i) {
// Implement circular array by modulo operation
// When i exceeds the tail of the array, return to the head
// When i exceeds the head of the array, return to the tail
return (i + capacity()) % capacity();
}
/* Front enqueue */
void pushFirst(int num) {
if (queSize == capacity()) {
cout << "Double-ended queue is full" << endl;
return;
}
// Move the front pointer one position to the left
// Implement front crossing the head of the array to return to the tail by modulo operation
front = index(front - 1);
// Add num to the front
nums[front] = num;
queSize++;
}
/* Rear enqueue */
void pushLast(int num) {
if (queSize == capacity()) {
cout << "Double-ended queue is full" << endl;
return;
}
// Calculate rear pointer, pointing to rear index + 1
int rear = index(front + queSize);
// Add num to the rear
nums[rear] = num;
queSize++;
}
/* Front dequeue */
int popFirst() {
int num = peekFirst();
// Move front pointer one position backward
front = index(front + 1);
queSize--;
return num;
}
/* Rear dequeue */
int popLast() {
int num = peekLast();
queSize--;
return num;
}
/* Access front element */
int peekFirst() {
if (isEmpty())
throw out_of_range("Double-ended queue is empty");
return nums[front];
}
/* Access rear element */
int peekLast() {
if (isEmpty())
throw out_of_range("Double-ended queue is empty");
// Calculate rear element index
int last = index(front + queSize - 1);
return nums[last];
}
/* Return array for printing */
vector<int> toVector() {
// Only convert elements within valid length range
vector<int> res(queSize);
for (int i = 0, j = front; i < queSize; i++, j++) {
res[i] = nums[index(j)];
}
return res;
}
};
/* Driver Code */
int main() {
/* Initialize double-ended queue */
ArrayDeque *deque = new ArrayDeque(10);
deque->pushLast(3);
deque->pushLast(2);
deque->pushLast(5);
cout << "Double-ended queue deque = ";
printVector(deque->toVector());
/* Access element */
int peekFirst = deque->peekFirst();
cout << "Front element peekFirst = " << peekFirst << endl;
int peekLast = deque->peekLast();
cout << "Back element peekLast = " << peekLast << endl;
/* Element enqueue */
deque->pushLast(4);
cout << "Element 4 enqueued at the tail, deque = ";
printVector(deque->toVector());
deque->pushFirst(1);
cout << "Element 1 enqueued at the head, deque = ";
printVector(deque->toVector());
/* Element dequeue */
int popLast = deque->popLast();
cout << "Deque tail element = " << popLast << ", after dequeuing from the tail";
printVector(deque->toVector());
int popFirst = deque->popFirst();
cout << "Deque front element = " << popFirst << ", after dequeuing from the front";
printVector(deque->toVector());
/* Get the length of the double-ended queue */
int size = deque->size();
cout << "Length of the double-ended queue size = " << size << endl;
/* Determine if the double-ended queue is empty */
bool isEmpty = deque->isEmpty();
cout << "Is the double-ended queue empty = " << boolalpha << isEmpty << endl;
return 0;
}