C Add polynomials example

#include <stdio.h>
 
struct Polynomial {
  int coeff;
  int exp;
};
 
struct Polynomial first[15], second[15], result[15];
 
void display (struct Polynomial poly[], int terms)
{
  int i;
  printf ("\n");
  for (i = 0; i < terms - 1; i++) {
    printf ("%dX^%d+ ", poly[i].coeff, poly[i].exp);
  }
  printf ("%dX^%d ", poly[i].coeff, poly[i].exp);
}
 
int readExpression (struct Polynomial poly[])
{
  int terms, i;
  printf ("\nNumber of terms: ");
  scanf ("%d", &terms);
  printf ("\nEnter the coeffecients and exponents in DESCENDING order");
  for (i = 0; i < terms; i++) {
    printf ("\nCoeffecient :");
    scanf ("%d", &poly[i].coeff);
    printf ("Exponent :");
    scanf ("%d", &poly[i].exp);
  }
  return terms;
}
 
int addExpressions (int firstCount, int secondCount)
{
  int i, j, k;
  i = 0;
  j = 0;
  k = 0;
  while (i < firstCount && j < secondCount) {
    if (first[i].exp == second[j].exp) {
      result[k].coeff = first[i].coeff + second[j].coeff;
      result[k].exp = first[i].exp;
      i++;
      j++;
      k++;
    }
    else if (first[i].exp > second[j].exp) {
      result[k].coeff = first[i].coeff;
      result[k].exp = first[i].exp;
      i++;
      k++;
    }
    else {
      result[k].coeff = second[i].coeff;
      result[k].exp = second[j].exp;
      j++;
      k++;
    }
  }
 
  while (i < firstCount) {
    result[k].coeff = first[i].coeff;
    result[k].exp = first[i].exp;
    k++;
    i++;
  }
 
  while (j < secondCount) {
    result[k].coeff = second[j].coeff;
    result[k].exp = second[j].exp;
    k++;
    j++;
  }
  return k;
}
 
int main ()
{
  int firstCount, secondCount, resultCount;
  printf ("\nFirst Expression:\n");
  firstCount = readExpression (first);
  printf ("\nSecond Expression:\n");
  secondCount = readExpression (second);
  printf ("\nFirst Expression");
  display (first, firstCount);
  printf ("\nSecond Expression");
  display (second, secondCount);
  resultCount = addExpressions (firstCount, secondCount);
  printf ("\nResultant Expression:\n");
  display (result, resultCount);
  return 0;
}