polyomial multiplication

rani.c

#include <stdio.h>
#include <stdlib.h>

typedef struct Node {
  int coeff;
  int exp;
  struct Node *next;
} node;


void append(node **head, int coeff, int exp) {
  if (coeff == 0) return; 

  node *new_node = (node *)malloc(sizeof(node));
  new_node->coeff = coeff;
  new_node->exp = exp;
  new_node->next = NULL;

  if (*head == NULL || (*head)->exp < exp) {
    new_node->next = *head;
    *head = new_node;
  } else {
    node *temp = *head;
    while (temp->next != NULL && temp->next->exp > exp)
      temp = temp->next;

    if (temp->next != NULL && temp->next->exp == exp) {
      temp->next->coeff += coeff;
      free(new_node);
    } else {
      new_node->next = temp->next;
      temp->next = new_node;
    }
  }
}

void print_poly(node *head) {
  if (head == NULL) {
    printf("0\n");
    return;
  }

  int first = 1;
  while (head != NULL) {
    if (!first) {
      printf(" %c ", (head->coeff > 0) ? '+' : '-');
    } else {
      if (head->coeff < 0) printf("-");
      first = 0;
    }

    int abs_coeff = (head->coeff < 0) ? -head->coeff : head->coeff;

    if (head->exp == 0)
      printf("%d", abs_coeff);
    else if (head->exp == 1)
      printf("%dx", abs_coeff);
    else
      printf("%dx^%d", abs_coeff, head->exp);

    head = head->next;
  }
  printf("\n");
}

node *multiply(node *p1, node *p2) {
  node *res = NULL;

  for (node *i = p1; i != NULL; i = i->next) {
    for (node *j = p2; j != NULL; j = j->next) {
      append(&res, i->coeff * j->coeff, i->exp + j->exp);
    }
  }

  return res;
}

void combine_like_terms(node **head) {
  node *ptr = *head, *prev = NULL;
  while (ptr != NULL) {
    if (ptr->coeff == 0) {
      if (prev == NULL) {
        *head = ptr->next;
        free(ptr);
        ptr = *head;
      } else {
        prev->next = ptr->next;
        free(ptr);
        ptr = prev->next;
      }
    } else {
      prev = ptr;
      ptr = ptr->next;
    }
  }
}

void free_poly(node *head) {
  node *temp;
  while (head != NULL) {
    temp = head;
    head = head->next;
    free(temp);
  }
}

int main() {
  node *p1 = NULL, *p2 = NULL;

  int n, coeff, exp;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d %d", &coeff, &exp);
    append(&p1, coeff, exp);
  }

  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    scanf("%d %d", &coeff, &exp);
    append(&p2, coeff, exp);
  }

  print_poly(p1);

  print_poly(p2);

  node *res = multiply(p1, p2);
  combine_like_terms(&res);

  print_poly(res);

  free_poly(p1);
  free_poly(p2);
  free_poly(res);

  return 0;
}