Adding two polynomials using Circular Linked List

Last Updated : 12 Jan, 2022

Given two polynomial numbers represented by a circular linked list, the task is to add these two polynomials by adding the coefficients of the powers of the same variable.

Note: In given polynomials, the term containing the higher power of x will come first.

Examples:

Input:
1st Number = 5x^2 * y^1 + 4x^1 * y^2 + 3x^1 * y^1 + 2x^1
2nd Number = 3x^1 * y^2 + 4x^1
Output:
5x^2 * y^1 + 7x^1 * y^2 + 3x^1 * y^1 + 6x^1
Explanation:
The coefficient of x^2 * y^1 in 1st numbers is 5 and 0 in the 2nd number. Therefore, sum of the coefficient of x^2 * Y^1 is 5.
The coefficient of x^1 * y^2 in 1st numbers is 4 and 3 in the 2nd number. Therefore, sum of the coefficient of x^1 * Y^2 is 7.
The coefficient of x^1 * y^1 in 1st numbers is 3 and 0 in the 2nd number. Therefore, sum of the coefficient of x^1 * Y^1 is 2.
The coefficient of x^1 * Y^0 in 1st numbers is 2 and 4 in the 2nd number. Therefore, sum of the coefficient of x^1 * Y^0 is 6.

Input:
1st Number = 3x^3 * y^2 + 2x^2 + 5x^1 * y^1 + 9y^1 + 2
2nd Number = 4x^3 * y^3 + 2x^3 * y^2 + 1y^2 + 3
Output:
4x^3 * y^3 + 5x^3 * y^2 + 2x^2 + 5x^1 * y^1 + 1y^2 + 9y^1 + 5

Approach: Follow the below steps to solve the problem:

Create two circular linked lists, where each node will consist of the coefficient, power of x, power of y and pointer to the next node.
Traverse both the polynomials and check the following conditions:
- If power of x of 1st polynomial is greater than power of x of second polynomial then store node of first polynomial in resultant polynomial and increase counter of polynomial 1.
- If power of x of 1st polynomial is less than power of x of second polynomial then store the node of second polynomial in resultant polynomial and increase counter of polynomial 2.
- If power of x of 1st polynomial is equal to power of x of second polynomial and power of y of 1st polynomial is greater than power of y of 2nd polynomial then store the node of first polynomial in resultant polynomial and increase counter of polynomial 1.
- If power of x of 1st polynomial is equal to power of x of second polynomial and power of y of 1st polynomial is equal to power of y of 2nd polynomial then store the sum of coefficient of both polynomial in resultant polynomial and increase counter of both polynomial 1 and polynomial 2.
If there are nodes left to be traversed in 1st polynomial or in 2nd polynomial then append them in resultant polynomial.
Finally, print the resultant polynomial.

Below is the implementation of the above approach:

C++

// C++ program to implement
// the above approach


#include <bits/stdc++.h>
using namespace std;


// Structure of a node
// in a circular linked list
struct Node {
    
    
    // Stores coefficient
    // of a node
    int coeff;
    
    
    // Stores power of'
    // variable x of a node
    int powx;
    
    
    // Stores power of
    // variable y of a node
    int powy;
    
    
    // Stores pointer 
    // to next node
    struct Node* next;
};


// Function to dynamically create a node
void create_node(int c, int p1, int p2, 
                        struct Node** temp)
{
    
    // Stores new node
    struct Node *r;
    
    
    // Stores temp node
    struct Node *z 
              = *temp;


    // Dynamically create a new node
    r = (struct Node*)malloc(
                  sizeof(struct Node));
      
                  
    // Update coefficient
    // of r              
    r->coeff = c;
    
    
    // Update power of 
    // variable x in r
    r->powx = p1;
    
    
    // Update power of 
    // variable y in r
    r->powy = p2;
    
    
    // If z is null
    if (z == NULL) {
        
        
        // Update temp node
        (*temp) = r;
        
        
        // Update next pointer
        // of temp node
        (*temp)->next = (*temp);
    }
    else {
        
        
        // Update next pointer
        // of z
        r->next = z->next;
        
        
        // Update next pointer
        // of z
        z->next = r;
        
        
        // Update temp Node
        (*temp) = r;
    }
}


// Function to add polynomial of two list
void add_poly(struct Node* poly1, 
    struct Node* poly2, struct Node** temp)
{
    

    // Stores head node of polynomial1
    struct Node *start1 = poly1;
    
    
    // Stores head node of polynomial1
    struct Node *start2 = poly2;
    
    
    // Update poly1
    poly1 = poly1->next;
    
    
    // Update poly2
    poly2 = poly2->next;


    // Traverse both circular linked list
    while ((poly1 != start1 &&
                     poly2 != start2)) {
                         
                         
        // Stores new node                 
        struct Node* r;
        
        
        // Stores temp node
        struct Node* z 
                 = *temp;
                 
        
        // Dynamically create a new node         
        r = (struct Node*)malloc(
                    sizeof(struct Node));
                    
                    
        // Update coefficient of r            
        r->coeff = 0;


        // If power of x of poly1 is
        // greater than power of x of poly2
        if (poly1->powx > poly2->powx) {
            
            
            // Update coefficient of r
            r->coeff = poly1->coeff;
            
            
            // Update of power of x in r
            r->powx = poly1->powx;
            
            
            // Update of power of y in r
            r->powy = poly1->powy;
            
            
            // Update poly1
            poly1 = poly1->next;
        }


        // If power of x of 1st polynomial is
        // less than power of x of 2nd poly
        else if (poly1->powx < poly2->powx) {
            
            
            // Update coefficient OF r
            r->coeff = poly2->coeff;
            
            
            // Update power of x in r
            r->powx = poly2->powx;
            
            
            // Update power of y in r
            r->powy = poly2->powy;
            
            
            // Update ploy2
            poly2 = poly2->next;
        }


        // If power of x of 1st polynomial is
        //  equal to power of x of 2nd poly
        else {
            
            
            // Power of y of 1st polynomial is
            // greater than power of y of poly2
            if (poly1->powy > poly2->powy) {
                
                
                // Update coefficient of r
                r->coeff = poly1->coeff;
                
                
                // Update power of x in r
                r->powx = poly1->powx;
                
                
                // Update power of y in r
                r->powy = poly1->powy;
                
                
                // Update poly1
                poly1 = poly1->next;
            }


            // If power of y of poly1 is 
            // less than power of y of ploy2
            else if (poly1->powy < 
                            poly2->powy) {
                
                
                // Update coefficient of r
                r->coeff = poly2->coeff;
                
                
                // Update power of x in r
                r->powx = poly2->powx;
                
                
                // Update power of y in r
                r->powy = poly2->powy;
                
                
                // Update poly2
                poly2 = poly2->next;
            }


            // If power of y of 1st poly is
            // equal to power of y of ploy2
            else {
                
                
                // Update coefficient of r
                r->coeff = poly2->coeff 
                         + poly1->coeff;
                         
                         
                // Update power of x in r         
                r->powx = poly1->powx;
                
                
                // Update power of y in r 
                r->powy = poly1->powy;
                
                
                // Update poly1
                poly1 = poly1->next;
                
                
                // Update poly2
                poly2 = poly2->next;
            }
        }
        
        
        // If z is null
        if (z == NULL) {
            
            
            // Update temp
            (*temp) = r;
            
            
            // Update next pointer
            // of temp
            (*temp)->next = (*temp);
        }
        else {
            
            
            // Update next pointer
            // of r
            r->next = z->next;
            
            
            // Update next pointer 
            // of z
            z->next = r;
            
            
            // Update temp
            (*temp) = r;
        }
    }
    
    
    // If there are nodes left to be  
    // traversed in poly1 or poly2 then
    // append them in resultant polynomial .
    while (poly1 != start1 ||
                    poly2 != start2) {
                        
                        
                        
        // If poly1 is not empty                
        if (poly1 != start1) {
            
            
            // Stores new node
            struct Node *r;
            
            
            // Stores temp node
            struct Node *z = *temp;
            
            
            // Create new node
            r = (struct Node*)malloc(
                        sizeof(struct Node));
                        
                        
            // Update coefficient or r
            r->coeff = poly1->coeff;
            
            
            // Update power of x in r
            r->powx = poly1->powx;
            
            
            // Update power of y in r
            r->powy = poly1->powy;
            
            
            // Update poly1
            poly1 = poly1->next;
            
            
            // If z is null
            if (z == NULL) {
                
                
                // Update temp
                (*temp) = r;
                
                
                // Update pointer 
                // to next node
                (*temp)->next = (*temp);
            }
            else {
                
                
                // Update next pointer
                // of r
                r->next = z->next;
                
                
                // Update next pointer of z
                z->next = r;
                
                
                // Update temp
                (*temp) = r;
            }
        }
        
        
        // If poly2 is not empty
        if (poly2 != start2) {
            
            
            // Stores new node
            struct Node *r;
            
            
            // Stores temp node
            struct Node *z = *temp;
            
            
            // Create new node
            r = (struct Node*)malloc(
                     sizeof(struct Node));
                 
                     
            // Update coefficient of z         
            z->coeff = poly2->coeff;
            
            
            // Update power of x in z
            z->powx = poly2->powx;
            
            
            // Update power of y in z
            z->powy = poly2->powy;
            
            
            // Update poly2
            poly2 = poly2->next;
            
            
            // If z is null
            if (z == NULL) {
                
                
                // Update temp
                (*temp) = r;
                
                
                // Update next pointer
                // of temp
                (*temp)->next = (*temp);
            }
            else {
                
                
                // Update next pointer
                // of r
                r->next = z->next;
                
                
                // Update next pointer 
                // of z
                z->next = r;
                
                
                // Update temp
                (*temp) = r;
            }
        }
    }
    
    
    // Stores new node
    struct Node *r;
    
    
    
    // Stores temp node
    struct Node *z = *temp;
    
    
    // Create new node
    r = (struct Node*)malloc(
         sizeof(struct Node));
         
    
    // Update coefficient of r     
    r->coeff = 0;
    

    // If power of x of start1 greater than
    // power of x of start2
    if (start1->powx > start2->powx) {
        
        
        // Update coefficient of r
        r->coeff = start1->coeff;
        
        
        // Update power of x in r
        r->powx = start1->powx;
        
        
        // Update power of y in r
        r->powy = start1->powy;
    }
    
    
    // If power of x of start1 less than
    // power of x of start2
    else if (start1->powx < start2->powx) {
        
        
        // Update coefficient of r
        r->coeff = start2->coeff;
        
        
        // Update power of x in r
        r->powx = start2->powx;
        
        
        // Update power of y in r
        r->powy = start2->powy;
    }
    
    
    // If power of x of start1 equal to
    // power of x of start2
    else {
        
        
        // If power of y of start1 greater than
        // power of y of start2
        if (start1->powy > start2->powy) {
            
            
            // Update coefficient of r
            r->coeff = start1->coeff;
            
            
            // Update power of x in r
            r->powx = start1->powx;
            
            
            // Update power of y in r
            r->powy = start1->powy;
        }
        
        
        // If power of y of start1 less than
        // power of y of start2
        else if (start1->powy < 
                           start2->powy) {
            
            
            // Update coefficient of r
            r->coeff = start2->coeff;
            
            
            // Update power of x in r
            r->powx = start2->powx;
            
            
            // Update power of y in r
            r->powy = poly2->powy;
        }
        
        
        // If power of y of start1 equal to
        // power of y of start2
        else {
            
            
            // Update coefficient of r
            r->coeff = start2->coeff 
                        + start1->coeff;
            
            
            // Update power of x in r
            r->powx = start1->powx;
            
            
            // Update power of y in r
            r->powy = start1->powy;
        }
    }
    
    
    // If z is null
    if (z == NULL) {
        
        
        // Update temp
        (*temp) = r;
        
        
        // Update next pointer 
        // of temp
        (*temp)->next = (*temp);
    }
    else {
        
        
        // Update next pointer of r
        r->next = z->next;
        
        
        // Update next pointer of z
        z->next = r;
        
        
        // Update temp
        (*temp) = r;
    }
}


// Display the circular linked list
void display(struct Node* node)
{
    
    // Stores head node of list
    struct Node* start = node;
    
    
    // Update node
    node = node->next;
    
    
    // Traverse the list
    while (node != start &&
            node->coeff != 0) {
                
                
        // Print coefficient of
        // current node        
        cout << node->coeff;
        
        
        // If power of variable x
        // is not zero
        if (node->powx != 0)
            cout << "x^" << node->powx;
            
        
        // If power of variable x
        // and y is not zero     
        if(node->powx != 0 &&
                 node->powy != 0) 
            cout<<" * ";  


        // If power of variable y
        // is not zero    
        if (node->powy != 0)
            cout << "y^" << node->powy;
            
            
        // Add next term of 
        // the polynomial    
        if (node != start &&
          node->next->coeff != 0) {
            cout << " + ";
        }
        
        
        // Update node
        node = node->next;
    }
    
    
    // Print coefficient of
    // current node 
    cout << node->coeff;
    
    
    // If power of variable x
    // is not zero
    if (node->powx != 0)
        cout << "x^" << node->powx;
        
    
    // If power of variable y
    // is not zero    
    if (node->powy != 0)
        cout << "y^" << node->powy;
    cout << "\n\n";
}


// Driver Code
int main()
{
    
    // Stores node of 
    // first polynomial
    struct Node *poly1 = NULL;
    
    
    // Stores node of 
    // second polynomial
    struct Node *poly2 = NULL;
    
    
    // Stores node of resultant 
    // polynomial
    struct Node *store = NULL;


    // Create first polynomial
    create_node(5, 2, 1, &poly1);
    create_node(4, 1, 2, &poly1);
    create_node(3, 1, 1, &poly1);
    create_node(2, 1, 0, &poly1);
    create_node(3, 0, 1, &poly1);
    create_node(2, 0, 0, &poly1);


    // Create second polynomial
    create_node(3, 1, 2, &poly2);
    create_node(4, 1, 0, &poly2);
    create_node(2, 0, 1, &poly2);
    create_node(6, 0, 0, &poly2);

    
    // Function call to add
    // two polynomial
    add_poly(poly1, poly2, &store);

    // Display polynomial 1
    cout << "Polynomial 1"
         << "\n";
    display(poly1);

    // Display polynomial 2
    cout << "Polynomial 2"
         << "\n";
    display(poly2);

    // Display final addition of 2-variable polynomial
    cout << "Polynomial after addition"
         << "\n";
    display(store);

    return 0;
}

Output

Polynomial 1
5x^2 * y^1 + 4x^1 * y^2 + 3x^1 * y^1 + 2x^1 + 3y^1 + 2

Polynomial 2
3x^1 * y^2 + 4x^1 + 2y^1 + 6

Polynomial after addition
5x^2 * y^1 + 7x^1 * y^2 + 3x^1 * y^1 + 6x^1 + 5y^1 + 8

Time Complexity: O(M + N), where M and N are number of nodes in the first and second lists respectively.
Auxiliary Space: O(M + N)

Adding two polynomials using Linked List

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Adding two polynomials using Circular Linked List

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