Fundamentals of Data Structure and Algorithm (Wang Zhuo) (8): Application of linear tables (union: no need for order, no repetition)

Table of contents

Union set: Merge of linear tables (no order, no repetition)

Linear table:

linked list:

---

PPT: Chapter 2 P173;

---

Union set: Merge of linear tables (no order, no repetition)

Linear table:

Status Union(Sqlist& A, Sqlist& B)//并集
{
    int len_A = A.length;
    int len_B = B.length;
    for (int i = 1; i <= len_B; i++)
    {
        Poly e=*A.elem;
        //这里只是给我们设定的元素e赋一个任意初值
        //只要保证e在初始化时由初值不为空即可
        //至于该e元素的内容是什么其实并没有什么所谓
        //因为后面我们总归是会改的
        GetElem(B, i, e);
        if (LocateElem(A, e))
            return ERROR;
        else
            ListInsert(A, ++len_A, e);
        //注意插入函数中输入的是位序，不是数组下标
    }
    return true;
}

Time complexity of the algorithm: O(ListLenth(La) * ListLength(Lb))

The last table A is the new table after the merger

---

linked list:

Status Union(Lnode& A, Lnode& B)
{
    for (int i = 1; i <= 求表长(&B); i++)
    {
        int len_A = 求表长(&A);
        Elemtype e;
        取第i个元素(&A, i, e);
        if (!LocateELem(&B, e))
            Listlnsert(&A, ++len_A, e);
    }
    return true;
}

Result: (default in (7): Summary: Run under the preset pre-statements in the definition and operation of linked lists and linear lists) 

The reason for this result is related to the statement defining the insertion function in the preceding statement:

Status Listlnsert(LinkList& L, int i, Elemtype e)

To be more precise: the problem stems from the fact that the type of "&A" we gave does not match the type of "LinkList& L" in the definition

Here, we make a systematic summary of LinkList & A and other formats:

 What does &A stand for? ?

Sqlist A: variable A of the linear table node type

Sqlist &A: It still represents the variable A of the node type of the linear table, but (just) represents the method of passing by value by reference

LinkList A: Pointer variable A whose target object is the node type of linear list

LinkList &A: It is still a pointer variable A indicating that the target object is a linear list node type

It just
means that the address is conveyed (delivered) using the value-by-reference method 

---

If you want the program to run normally, there are two ways to modify it:

1：

Modify the function body of the <insert> function: (the <merge> function does not need to be modified at this time)

Change the "declaration" (outside the function body) part of the merged function to read:

Status Listlnsert(LinkList L, int i, Elemtype e)

At this point, the preconditions (simplest version) required by the merge function are:

//链表的定义及其基础操作
#include<iostream>
using namespace std;
#include<stdlib.h>//存放exit

#define TRUE        1
#define FALSE       0
#define OK          1
#define ERROR       0
#define INFEASIBLE  -1
#define OVERFLOW   -2   

#define MAXlength 100  //初始大小为100，可按需修改

typedef int Status;         //函数调用状态

struct K
{
    float a;
    int b;
    string c;
    bool operator==(K& t)
    {
        return t.a == a && t.b == b;
        //&& t.c = c;
    }
    bool operator!=(K& t)
    {
        return t.a != a || t.b != b;
        //|| t.c = c;
    }
};
typedef K Elemtype;         //函数调用状态

struct Lnode
    //node:结; 结点;
{
    Elemtype data;
    Lnode* next;
};
typedef Lnode* LinkList;

Status 链表是否为空(LinkList L)
{
    if (L->next)
        return true;
    else
        return false;
}
Status 求表长(LinkList L)
{
    if (链表是否为空(L))
        cerr << "链表为空" << endl;
    LinkList p = L->next;
    //特别注意：因为这里从首元结点开始算起（计算）
    //所以：L->next;
    int i = 0;
    while (p)//不要写成if
    {
        p = p->next;
        i++;
    }
    //cout << "表长为：  " << i << endl;
    return i;
}

Status 取第i个元素(LinkList L, int i, Elemtype e)
{// GetElem“i”
    LinkList p;
    p = L->next;
    int j = 1;
    while (p && i > j)
    {
        p = p->next;
        j++;
    }
    if (i < 0 || i < j || !p)
        return false;
    e = p->data;
    return true;
}

Status LocateELem(LinkList L, Elemtype e)
{
    //在线性表L中查找值为e的数据元素
    //找到，则返回L中值为e的数据元素的地址，查找失败返回NULL
    auto p = L->next; int i = 1;
    while (p && p->data != e)
    {
        i++;
        if (e == p->data)
        {
            cout << "地址为：  " << p << ";" << endl;
            cout << "位置序号为：  " << i << ";" << endl;
        }
        p = p->next;
    }
    if (p == NULL)
        return NULL;
    return true;
}

Status Listlnsert(LinkList L, int i, Elemtype e)
{//插入（把元素e插到第i个位置结点上）
    auto p = L; int j = 0;
    while (p && j < i - 1)
    {
        p = p->next; ++j;
    }
    if (!p || j > i - 1)
        return false;
    auto s = new Lnode;
    s->data = e;
    s->next = p->next;
    p->next = s;
    return true;
}//Listlnsert_L

---

2:
Modify the function body of the <merge> function: (when the preceding statement remains unchanged and does not need to be changed)

Status Union(Lnode& A, Lnode& B)
{
    for (int i = 1; i <= 求表长(&B); i++)
    {
        int len_A = 求表长(&A);
        Elemtype e;
        LinkList p = &A;
        取第i个元素(&A, i, e);
        if (!LocateELem(&B, e))
            Listlnsert(p, ++len_A, e);
    }
    return true;
}

---

Then at this time, an interesting (very strange) phenomenon (situation) happened to me

question:

Why does the type of "&A" in the front and the "LinkList& L" in the definition not match

But as long as we put "&A" into a new variable of this type, let the information be executed in the program in the form of a variable

It's obviously the same thing (&A) put in, so why (how) can the program run when it turns out? ? ?