121 lines
2.5 KiB
C++
121 lines
2.5 KiB
C++
/**
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* File: linkedlist_queue.cpp
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* Created Time: 2022-11-25
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* Author: krahets (krahets@163.com)
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*/
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#include "../utils/common.hpp"
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/* 基于链表实现的队列 */
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class LinkedListQueue {
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private:
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ListNode *front, *rear; // 头节点 front ，尾节点 rear
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int queSize;
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public:
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LinkedListQueue() {
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front = nullptr;
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rear = nullptr;
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queSize = 0;
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}
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~LinkedListQueue() {
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// 遍历链表删除节点，释放内存
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freeMemoryLinkedList(front);
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}
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/* 获取队列的长度 */
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int size() {
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return queSize;
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}
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/* 判断队列是否为空 */
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bool isEmpty() {
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return queSize == 0;
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}
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/* 入队 */
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void push(int num) {
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// 在尾节点后添加 num
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ListNode *node = new ListNode(num);
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// 如果队列为空，则令头、尾节点都指向该节点
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if (front == nullptr) {
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front = node;
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rear = node;
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}
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// 如果队列不为空，则将该节点添加到尾节点后
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else {
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rear->next = node;
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rear = node;
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}
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queSize++;
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}
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/* 出队 */
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int pop() {
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int num = peek();
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// 删除头节点
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ListNode *tmp = front;
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front = front->next;
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// 释放内存
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delete tmp;
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queSize--;
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return num;
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}
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/* 访问队首元素 */
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int peek() {
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if (size() == 0)
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throw out_of_range("队列为空");
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return front->val;
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}
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/* 将链表转化为 Vector 并返回 */
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vector<int> toVector() {
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ListNode *node = front;
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vector<int> res(size());
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for (int i = 0; i < res.size(); i++) {
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res[i] = node->val;
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node = node->next;
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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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int main() {
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/* 初始化队列 */
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LinkedListQueue *queue = new LinkedListQueue();
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/* 元素入队 */
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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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cout << "队列 queue = ";
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printVector(queue->toVector());
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/* 访问队首元素 */
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int peek = queue->peek();
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cout << "队首元素 peek = " << peek << endl;
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/* 元素出队 */
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peek = queue->pop();
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cout << "出队元素 pop = " << peek << "，出队后 queue = ";
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printVector(queue->toVector());
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/* 获取队列的长度 */
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int size = queue->size();
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cout << "队列长度 size = " << size << endl;
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/* 判断队列是否为空 */
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bool empty = queue->isEmpty();
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cout << "队列是否为空 = " << empty << endl;
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// 释放内存
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delete queue;
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return 0;
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}
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