[cpp][data_structure]: queue -- user defined( bug )

[cpp][data_structure]:   queue  --  user defined( bug )

 

 

 

 

一、示意

 

 

 

 

 

二、源代码中存在的问题

 

　　1、　　有问题；在pop()中front指针设置有问题。

 

 

 

 

三、源码

#include <iostream>
#include <string>


struct unit
{
// functions
    unit(std::string s) { data = s; }

// data
    unit* front = NULL;
    unit* back = NULL;
    std::string data = "";
};


class queue
{
public:

    queue()
    {
        top = new unit( sinit );        // first object of unit, named "first_object", it has a vaule of "sinit"
        init = top ;
        bottom = top ;
        size++  ;
    }

    ~queue()
    {
        std::cout << "\n[queue_class]#\t~queue()" << std::endl; 
    }

    void push(std::string data)
    {
        unit* keep = bottom;
        
        bottom = new unit( data );
        bottom->front = keep;
        keep->back = bottom;

        size++ ;
        //std::cout << "[queue:c_push:f]#\t" << data << std::endl;
    }

    void pop()
    {
        unit* keep = top;
        
        if ( size == -1 )
        {
            this  ->  ~queue();     // destroy the current object by ' this ';  very funny; 
            std::cout << "\nERROR[queue:c_pop:f]#\tqueue out of range. \n" << std::endl ;
            
            exit(1);
        }
        else
        {
            if ( keep->data == sinit )
            {
                top = top->back ;
                unit* keep2 = top;
                size--  ;
                delete  keep;
                
                keep = keep2 ;
            }
            
            std::cout << "[queue:c_pop:f]#\t" << keep->data << std::endl;
            
            top = top->back ;
            size--  ;
            delete  keep;
        }
    }

    int getsize()
    {
        return  size;    
    }

    void out()
    {
        int i = 0;
        for(  unit* pt = top;  i <= size;  pt = pt->back  )
        {
            if ( pt->data == sinit )
            {
                i++ ;
                continue;
            }
            std::cout << "[queue:c_out:f]#\tdata(" << i++ << "/" << size << ")\t:=\t" << pt->data << std::endl;
        }    
    }

private:

// data
    const std::string sinit = "initial queue";    // initialize first object of unit
    int size = -1;    
    unit* init = NULL;
    unit* top = NULL;
    unit* bottom = NULL;
};


// test part
int main()
{
    queue q;
    q.push("tangxuanzang");
    q.push("sunwukong");
    q.push("zhuwuneng");
    q.push("shawujing");
    
    q.out();
    
    q.pop();    // pop "tangxuanzang" ;
    //q.out();

    q.pop();    // pop "sunwukong" ;
    //q.out();
    
    q.pop();    // pop "zhuwuneng" ;
    q.out();
    
    q.pop();    // pop "shawujing" ;
    //q.out();
    
    q.pop();    // out of range of queue ;
    //q.out();

    return 0;
}

 

 

 

四、运行结果

g++ -std=c++20 -O2 -Wall -pedantic -pthread main.cpp && ./a.out


[queue:c_out:f]#    data(1/4)    :=    tangxuanzang
[queue:c_out:f]#    data(2/4)    :=    sunwukong
[queue:c_out:f]#    data(3/4)    :=    zhuwuneng
[queue:c_out:f]#    data(4/4)    :=    shawujing
[queue:c_pop:f]#    tangxuanzang
[queue:c_pop:f]#    sunwukong
[queue:c_pop:f]#    zhuwuneng
[queue:c_out:f]#    data(0/0)    :=    shawujing
[queue:c_pop:f]#    shawujing

[queue_class]#    ~queue()

ERROR[queue:c_pop:f]#    queue out of range. 

 

 

 

五、参考资料

 

　　1、　　数据结构与算法　　--　　https://www.runoob.com/data-structures/data-structures-tutorial.html

 

　　2、　　cpp在线工具　　--　　https://coliru.stacked-crooked.com/