111 lines
2.6 KiB
Dart
111 lines
2.6 KiB
Dart
/**
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* File: array_queue.dart
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* Created Time: 2023-03-28
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* Author: liuyuxin (gvenusleo@gmail.com)
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*/
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/* Queue class based on circular array */
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class ArrayQueue {
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late List<int> _nums; // Array used to store queue elements
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late int _front; // Front pointer, pointing to the front element
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late int _queSize; // Queue length
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ArrayQueue(int capacity) {
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_nums = List.filled(capacity, 0);
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_front = _queSize = 0;
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}
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/* Get the capacity of the queue */
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int capaCity() {
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return _nums.length;
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}
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/* Get the length of the queue */
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int size() {
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return _queSize;
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}
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/* Determine if the queue is empty */
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bool isEmpty() {
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return _queSize == 0;
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}
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/* Enqueue */
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void push(int _num) {
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if (_queSize == capaCity()) {
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throw Exception("Queue is full");
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}
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// Calculate rear pointer, pointing to rear index + 1
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// Use modulo operation to wrap the rear pointer from the end of the array back to the start
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int rear = (_front + _queSize) % capaCity();
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// Add _num to the back of the queue
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_nums[rear] = _num;
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_queSize++;
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}
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/* Dequeue */
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int pop() {
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int _num = peek();
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// Move front pointer one position backward, returning to the head of the array if it exceeds the tail
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_front = (_front + 1) % capaCity();
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_queSize--;
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return _num;
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}
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/* Access front element */
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int peek() {
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if (isEmpty()) {
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throw Exception("Queue is empty");
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}
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return _nums[_front];
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}
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/* Return Array */
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List<int> toArray() {
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// Only convert elements within valid length range
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final List<int> res = List.filled(_queSize, 0);
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for (int i = 0, j = _front; i < _queSize; i++, j++) {
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res[i] = _nums[j % capaCity()];
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}
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return res;
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}
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}
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/* Driver Code */
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void main() {
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/* Initialize queue */
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final int capacity = 10;
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final ArrayQueue queue = ArrayQueue(capacity);
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/* Element enqueue */
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queue.push(1);
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queue.push(3);
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queue.push(2);
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queue.push(5);
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queue.push(4);
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print("Queue queue = ${queue.toArray()}");
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/* Access front element */
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final int peek = queue.peek();
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print("Front element peek = $peek");
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/* Element dequeue */
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final int pop = queue.pop();
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print("Dequeue element pop = $pop, queue after dequeue = ${queue.toArray()}");
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/* Get queue length */
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final int size = queue.size();
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print("Queue length size = $size");
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/* Determine if the queue is empty */
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final bool isEmpty = queue.isEmpty();
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print("Is the queue empty = $isEmpty");
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/* Test circular array */
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for (int i = 0; i < 10; i++) {
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queue.push(i);
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queue.pop();
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print("After the $i-th round of enqueue + dequeue, queue = ${queue.toArray()}");
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}
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}
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