C++如何使用链表添加多项式

Question

Take a look at the code, what am I doing wrong in the operator overloading while adding polynomials (lists)? It's not printing the desired answer. eg

P1: 5x^12 + 2x^9 + 4x^7 + 6x^6 + 1x^3

P2: 7x^8 + 2x^7 + 8x^6 + 6x^4 + 2x^2 + 3^x + 40

Answer: 5x^12 + 2x^9 + 7x^8 + 6x^7 + 14x^6 + 6x^4 + 1x^3 + 2x^2 + 3^x + 40

What is the correct way to add them?

#include <stdio.h>
#include <iostream>

using namespace std;

//Node is defined
class node {
public:
    //value will contain data
    int value1;
    int value2;
    //next stores location
    node *next;

    //Default Constructor
    node()
    {
        value1 = 0;
        value2 = 0;
        next = NULL;
    }
};

//mylist is defined
class mylist {
public:

    //head will keep notice of beginning of the list
    node* head;

    //track number of nodes
    int count = 0;

    //default constructor
    mylist() {}

    //constructor


    //insert at beginning
    void insert_at_beginning(int new_value1, int new_value2)
    {
        //creating new node
        node *new_node = new node();

        //increasing count
        count++;

        //copying value to new_node
        new_node->value1 = new_value1;
        new_node->value2 = new_value2;
        //pointing head to new_node when we have empty list
        if (head == NULL)
        {
            head = new_node;
        }
        //when list isn't empty
        else
        {
            /* new_node->next points where heads points*/
            new_node->next = head;

            /* Updating head node to point to newly added node*/
            head = new_node;
        }
    }

    //inert node or item at Specific Location
    void insert_at_loc(int location, double new_val1, double new_val2)
    {
        //temp node to keep track of location
        node* temp = head;

        //x acts as counter
        int x = count;

        //check if location is valid or not
        if (count < location) {
            cout << ("\n --Invalid Location Node Can't be Added at this Location -- ") << endl;
        }
        else {
            //traversing thourgh list finding specific location to add node
            while (x != NULL) {
                if (x == (count - location + 2)) {

                    //found location now creating new node and fixing links
                    node *new_node1 = new node();

                    //increasing count
                    count++;
                    new_node1->value1 = new_val1;
                    new_node1->value2 = new_val2;
                    //new_node1->next points to temp->next
                    new_node1->next = temp->next;

                    //temp-next points to newly added new_node1
                    temp->next = new_node1;
                }
                else {
                    temp = temp->next;
                }
                x--;
            }

        }

    }

    //printing list
    void printList()
    {
        cout << endl << "Linked-List : ";
        node* temp = head;

        while (temp != NULL) {
            cout << temp->value2 << "x^" << temp->value1 << "--> ";
            temp = temp->next;
        }
    }

    void del(int del_loc) {

        //temp1 to keep track location
        node* t1 = head;

        //if location is head 
        if (del_loc <= 1) {
            head = t1->next;

            //free memory
            delete(t1);

            //decrementing count
            count--;
        }
        //location is other than head
        else if (del_loc < count) {
            for (int y = count; y != (count - del_loc + 2); y--) {
                t1 = t1->next;
            }
            //fixing links
            node* t2 = t1->next;
            t1->next = t2->next;

            //free memory
            delete t2;

            //decrementing count
            count--;
        }
        else {
            cout << "\n **Sorry Location Doesn't Exist **" << endl;
        }
    }

    //Display Number of Nodes
    void count_func() {
        cout << "\n\n No. of Nodes Present in Linked List : " << count << endl;
    }

    void mylist::operator+=(const mylist& l2) {
        node *temp_l1 = head;
        node *temp_l2 = l2.head;
        mylist answer;

        while ((temp_l1 != NULL) && (temp_l2 != NULL)) {
            if (temp_l1 != NULL && temp_l2 == NULL) {
                answer.insert_at_beginning(temp_l1->value1, temp_l1->value2);
                temp_l1 = temp_l1->next;
            }

            if (temp_l1 == NULL && temp_l2 != NULL) {
                answer.insert_at_beginning(temp_l2->value1, temp_l2->value2);
                temp_l2 = temp_l2->next;
            }

            if (temp_l1 != NULL && temp_l2 != NULL) {
                if (temp_l1->value1 == temp_l2->value1) {
                    answer.insert_at_beginning(temp_l1->value1, (temp_l1->value2+temp_l2->value2) );
                    if (temp_l1 != NULL)
                        temp_l1 = temp_l1->next;
                    if (temp_l2 != NULL)
                        temp_l2 = temp_l2->next;
                }
                else if (temp_l1->value1 > temp_l2->value1 ) {
                    answer.insert_at_beginning(temp_l1->value1, temp_l1->value2);
                    temp_l1 = temp_l1->next;

                }
                else if (temp_l1->value1 < temp_l2->value1) {
                    answer.insert_at_beginning(temp_l2->value1, temp_l2->value2);
                    temp_l2 = temp_l2->next;

                }
            }
        }
        node *temp_ans = answer.head;
        while (temp_ans != NULL) {
            cout << temp_ans->value2 << "z^" << temp_ans->value1 << "--> ";
            temp_ans = temp_ans->next;
        }

    }
};



int main() {

    //creating linked_list
    mylist linked_list;
    mylist linked_list_1;
    mylist linked_list_2;
    mylist linked_list_ans;
    int menu = 0;

    int list_1_exp = 0;
    int list_1_exp_check = -100;
    double list_1_coef;
    char list_1_menu = 0;

    cout << " *********************** Enter 1st Polynomial in Ascending Order w.r.t Exponential *********************** " << endl;

    while (list_1_menu != 'E' || list_1_menu != 'e') {

        cout << " \nWould you like to add term in 1st Polynomial (y or n): " << endl;
        cout << " Enter 'E' to exit: " << endl;
        cout << " Your Choice: ";
        cin >> list_1_menu;

        if (list_1_menu == 'Y' || list_1_menu == 'y') {

            cout << "Enter the Exponent for the term : ";
            cin >> list_1_exp;

            if (list_1_exp > list_1_exp_check || list_1_exp_check == -100) {
                list_1_exp_check = list_1_exp;
            }
            else if (list_1_exp <= list_1_exp_check) {
                cout << " Invalid Exponent for the term (can't be Equal or Less than Last Term) " << endl;
                cout << " Please Enter Exponent Greater than " << list_1_exp_check << endl;
                cout << " Enter the Exponent for the term : ";
                cin >> list_1_exp;
                list_1_exp_check = list_1_exp;
            }

            cout << "Enter the Coefficent for the term : ";
            cin >> list_1_coef;

            linked_list_1.insert_at_beginning(list_1_exp, list_1_coef);

            linked_list_1.printList();
            cout << " NULL" << endl << endl;
        }
        else if (list_1_menu == 'N' || list_1_menu == 'n') {
            break;
        }
        else if (list_1_menu == 'E' || list_1_menu == 'e') {
            break;
        }
    }

    //priting list
    linked_list_1.printList();
    cout << " NULL" << endl << endl;

    int list_2_exp = 0;
    int list_2_exp_check = -100;
    double list_2_coef;
    char list_2_menu = 0;

    cout << " \n *********************** Enter 2nd Polynomial in Ascending Order w.r.t Exponential ***********************" << endl;

    while (list_2_menu != 'E' || list_2_menu != 'e') {

        cout << " \nWould you like to add term in 2nd Polynomial (y or n): " << endl;
        cout << " Enter 'E' to exit: " << endl;
        cout << " Your Choice: ";
        cin >> list_2_menu;

        if (list_2_menu == 'Y' || list_2_menu == 'y') {

            cout << "Enter the Exponent for the term : ";
            cin >> list_2_exp;

            if (list_2_exp > list_2_exp_check || list_2_exp_check == -100) {
                list_2_exp_check = list_2_exp;
            }
            else if (list_2_exp <= list_1_exp_check) {
                cout << " Invalid Exponent for the term (can't be Equal or Less than Last Term) " << endl;
                cout << " Please Enter Exponent Greater than " << list_2_exp_check << endl;
                cout << " Enter the Exponent for the term : ";
                cin >> list_2_exp;
                list_2_exp_check = list_2_exp;
            }

            cout << "Enter the Coefficent for the term : ";
            cin >> list_2_coef;

            linked_list_2.insert_at_beginning(list_2_exp, list_2_coef);

            linked_list_2.printList();
            cout << " NULL" << endl << endl;
        }
        else if (list_2_menu == 'N' || list_2_menu == 'n') {
            break;
        }
        else if (list_2_menu == 'E' || list_2_menu == 'e') {
            break;
        }
    }

    //priting list
    linked_list_2.printList();
    cout << " NULL" << endl << endl;

    linked_list_1.printList();
    cout << " NULL" << endl << endl;


    cout << " Addition " << endl;

    linked_list_1 += (linked_list_2);


    cout << "\nFinal List" << endl;
    linked_list_ans.printList();


    //program success
    system("pause");
    return 0;

}

I think that logic I'm trying for addition makes sense but it's not working. In the majority of cases it works as in if I have equal terms in the polynomial with the same degrees. It works fine for that but not for all cases. Please help!

Answer 1

Why not keep it simple instead:

Create a map<int, int> . Traverse through P1 and P2, insert indices as key and put coefficient as value . Increment the value of entry if the index or power already exist in the map, else create new entry with the index as key . After finishing the traversal of both P1 and P2, the map will compose of entries with index as key and sum of coefficients for each power/index in P1 and P2 as corresponding value.

Answer 2

The loop condition (temp_l1 != NULL) && (temp_l2 != NULL) guarantees that temp_l1 != NULL && temp_l2 == NULL and temp_l1 == NULL && temp_l2 != NULL are always false, so the bodies of corresponding if s are never executed. Take them out of the loop (and convert them to loops of course).

PS: to quickly find problems like this, use a debugger.