Using pointers in C

Modify the rain program in L isting   10.7    so that it does the calculations using pointers instead of subscripts. (You still have to declare and initialize the array.)

10.7

/* rain.c -- finds yearly totals, yearly average, and monthly

average for several years of rainfall data */

#include <stdio.h>

#define MONTHS 12 // number of months in a year

#define YEARS 5  // number of years of data

int main(void)

{

 // initializing rainfall data for 2000 - 2004

 const float rain[YEARS][MONTHS] =

 {

  { 4.3, 4.3, 4.3, 3.0, 2.0, 1.2, 0.2, 0.2, 0.4, 2.4, 3.5, 6.6 },

  { 8.5, 8.2, 1.2, 1.6, 2.4, 0.0, 5.2, 0.9, 0.3, 0.9, 1.4, 7.3 },

  { 9.1, 8.5, 6.7, 4.3, 2.1, 0.8, 0.2, 0.2, 1.1, 2.3, 6.1, 8.4 },

  { 7.2, 9.9, 8.4, 3.3, 1.2, 0.8, 0.4, 0.0, 0.6, 1.7, 4.3, 6.2 },

  { 7.6, 5.6, 3.8, 2.8, 3.8, 0.2, 0.0, 0.0, 0.0, 1.3, 2.6, 5.2 }

 };

 int year, month;

 float subtot, total;

 printf(" YEAR RAINFALL (inches)\n");

 for (year = 0, total = 0; year < YEARS; year++)

 { // for each year, sum rainfall for each month

  for (month = 0, subtot = 0; month < MONTHS; month++)

   //subtot += rain[year][month];

   subtot += *(*(rain + year) + month);

  printf("%5d %15.1f\n", 2000 + year, subtot);

  total += subtot; // total for all years

 }

 printf("\nThe yearly average is %.1f inches.\n\n",

  total / YEARS);

 printf("MONTHLY AVERAGES:\n\n");

 printf(" Jan Feb Mar Apr May Jun Jul Aug Sep Oct ");

 printf(" Nov Dec\n");

 for (month = 0; month < MONTHS; month++)

 { // for each month, sum rainfall over years

  for (year = 0, subtot = 0; year < YEARS; year++)

   //subtot += rain[year][month];

   subtot += *(*(rain + year) + month);

  printf("%4.1f ", subtot / YEARS);

 }

 printf("\n");

 return 0;

}