队列的链表实现 题目（难度1/10）

C++数据结构与算法 目录

队列介绍

队列这种容器，就像大家排队上公交车一样。

第一个来到的人排在最前面；

最后来的排在最后面；

第一个先上车（离开队列）；

队列的接口

队列是有如下接口的容器：

class Queue
{
public:
    const int& first(void) const;//队列的对头（第一个元素），最先进队列的元素
    inline bool empty(void) const;//判断队列里是否没有元素（空队列）
    inline size_t size(void) const;//返回队列元素数量
    void enqueue(const int& item);//将元素item进队列
    void dequeue(void);//将对头（队列的第一个元素）出队列（从队列中删除）
    void clear(void);//清空队列中的所有元素

实现思路

由于双链表的接口覆盖了队列的接口，所以可以使用双链表来实现一个队列。

这样就可以在双链表外面封装出一个队列的类。

在实现的时候，队列的接口只需要调用双链表的接口即可。

题目如下

#include <iostream>
#include <iomanip>
#include <list>
using namespace std;

//------下面的代码是用来测试你的代码有没有问题的辅助代码，你无需关注------
#include <algorithm>
#include <cstdlib>
#include <iostream> 
#include <vector>
#include <utility>
using namespace std;
struct Record { Record(void* ptr1, size_t count1, const char* location1, int line1, bool is) :ptr(ptr1), count(count1), line(line1), is_array(is) { int i = 0; while ((location[i] = location1[i]) && i < 100) { ++i; } }void* ptr; size_t count; char location[100] = { 0 }; int line; bool is_array = false; bool not_use_right_delete = false; }; bool operator==(const Record& lhs, const Record& rhs) { return lhs.ptr == rhs.ptr; }std::vector<Record> myAllocStatistic; void* newFunctionImpl(std::size_t sz, char const* file, int line, bool is) { void* ptr = std::malloc(sz); myAllocStatistic.push_back({ ptr,sz, file, line , is }); return ptr; }void* operator new(std::size_t sz, char const* file, int line) { return newFunctionImpl(sz, file, line, false); }void* operator new [](std::size_t sz, char const* file, int line)
{
    return newFunctionImpl(sz, file, line, true);
}void operator delete(void* ptr) noexcept { Record item{ ptr, 0, "", 0, false }; auto itr = std::find(myAllocStatistic.begin(), myAllocStatistic.end(), item); if (itr != myAllocStatistic.end()) { auto ind = std::distance(myAllocStatistic.begin(), itr); myAllocStatistic[ind].ptr = nullptr; if (itr->is_array) { myAllocStatistic[ind].not_use_right_delete = true; } else { myAllocStatistic[ind].count = 0; }std::free(ptr); } }void operator delete[](void* ptr) noexcept { Record item{ ptr, 0, "", 0, true }; auto itr = std::find(myAllocStatistic.begin(), myAllocStatistic.end(), item); if (itr != myAllocStatistic.end()) { auto ind = std::distance(myAllocStatistic.begin(), itr); myAllocStatistic[ind].ptr = nullptr; if (!itr->is_array) { myAllocStatistic[ind].not_use_right_delete = true; } else { myAllocStatistic[ind].count = 0; }std::free(ptr); } }
#define new new(__FILE__, __LINE__)
struct MyStruct { void ReportMemoryLeak() { std::cout << "Memory leak report: " << std::endl; bool leak = false; for (auto& i : myAllocStatistic) { if (i.count != 0) { leak = true; std::cout << "leak count " << i.count << " Byte" << ", file " << i.location << ", line " << i.line; if (i.not_use_right_delete) { cout << ", not use right delete. "; }	cout << std::endl; } }if (!leak) { cout << "No memory leak." << endl; } }~MyStruct() { ReportMemoryLeak(); } }; static MyStruct my; void check_do(bool b, int line = __LINE__) { if (b) { cout << "line:" << line << " Pass" << endl; } else { cout << "line:" << line << " Ohh! not passed!!!!!!!!!!!!!!!!!!!!!!!!!!!" << " " << endl; exit(0); } }
#define check(msg)  check_do(msg, __LINE__);
//------上面的代码是用来测试你的代码有没有问题的辅助代码，你无需关注------

class Queue
{
public:
    inline const int& first(void) const;
    inline bool empty(void) const;
    inline size_t size(void) const;
    void enqueue(const int& _item);
    void dequeue(void);
    void clear(void);
private:
    //使用双链表实现队列
    std::list<int> m_queue;
};

inline const int& Queue::first(void) const
{
    int a = 0;
    return a;
}

bool Queue::empty(void) const
{
    return false;
}

void Queue::clear(void)
{
}

size_t Queue::size(void) const
{
    return -1;
}

void Queue::enqueue(const int& _item)
{
}

void Queue::dequeue(void)
{
}

int main(int argc, char** argv)
{
    //test clear
    {
        Queue s;
        check(s.size() == 0);
        check(s.empty());
        s.enqueue(1);
        check(s.size() == 1);
        check(s.empty() == false);
        s.clear();
        check(s.size() == 0);
        check(s.empty());
    }
    //test first
    {
        Queue q;
        check(q.size() == 0);
        q.enqueue(1);
        check(q.size() == 1);
        auto q2 = q;
        check(q2.size() == 1);
        q = q2;
        q.enqueue(2);
        auto first = q2.first();
        check(first == 1);
        check(q.size() == 2);
        check(q.first() == 1);
        q.clear();
        check(q.size() == 0 && q.empty());
    }
    //test enqueue dequeue
    {
        Queue q;
        for (size_t i = 0; i < 10; i++)
        {
            q.enqueue(i);
        }
        int i = 0;
        while (!q.empty())
        {
            check(q.first() == i++)
                q.dequeue();
        }
        check(q.size() == 0 && q.empty());
    }
}

预期输出如下

line:71 Pass
line:72 Pass
line:74 Pass
line:75 Pass
line:77 Pass
line:78 Pass
line:83 Pass
line:85 Pass
line:87 Pass
line:91 Pass
line:92 Pass
line:93 Pass
line:95 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:107 Pass
line:110 Pass
Memory leak report:
No memory leak.