I need help finding the answer to Exercise 4, in Chapter 9 of Stephen Kochan\'s

Question

I need help finding the answer to Exercise 4, in Chapter 9 of Stephen Kochan's programming in C. It was recommended by my instructor to use a struct for the date to complete this exercise.

Using the following formula:

N = 1461 × f( year, month) / 4 + 153 × g( month) / 5 + day

where:

If you take the value of N and subtract 621,049 from it, and then take that result modulo 7, you get a number from 0 to 6 that represents the day of the week (Sunday through Saturday, respectively) on which the particular day falls. For example, the value of N computed for August 8, 2004, is 732,239 as derived previously. 732,239 – 621,049 gives 111,190, and 111,190 % 7 gives 2, indicating that this date falls on a Tuesday. Develop a program that displays the day of the week on which a particular date entered by the user falls. Make certain that the program displays the day of the week in English (such as “Monday”).

Explanation / Answer

#include <stdio.h>

struct Date {
    int day;
    int month;
    int year;
};

int fnF(int year, int month) {
    return month <=2 ? (year-1) : year;
}

int fnG(int month) {
    return month <=2 ? (month+1) : month;
}

void printDay(int N) {
    int day = N % 7;
    if(day == 0)
        printf("Sunday");
    if(day == 1)
    printf("Monday");
    if(day == 2)
    printf("Tueday");
    if(day == 3)
    printf("Wedday");
    if(day == 4)
    printf("Thuday");
    if(day == 5)
    printf("Friday");
    if(day == 6)
    printf("Satday");
}

int calculateN(struct Date date) {
    int num;
    int fnFVal = fnF(date.year, date.month);
    int fnGval = fnG(date.month);
    num = (1461 * fnFVal) / 4 + (153 * fnGval) / 5 + date.day;
    return num;
}


int main()
{
    struct Date date;
  
  
    int day, month, year;
    printf("Enter Day :");
    scanf("%d",&day);
    printf("Enter Month :");
    scanf("%d",&month);
    printf("Enter Year :");
    scanf("%d",&year);
    date.day = day;
    date.month = month;
    date.year = year;
  
    int N = calculateN(date);
  
    printDay(N);
    return 0;
}#include <stdio.h>

#include <stdio.h>

struct Date {
    int day;
    int month;
    int year;
};

int fnF(int year, int month) {
    return month <=2 ? (year-1) : year;
}

int fnG(int month) {
    return month <=2 ? (month+1) : month;
}

void printDay(int N) {
    int day = N % 7;
    if(day == 0)
        printf("Sunday");
    if(day == 1)
    printf("Monday");
    if(day == 2)
    printf("Tueday");
    if(day == 3)
    printf("Wedday");
    if(day == 4)
    printf("Thuday");
    if(day == 5)
    printf("Friday");
    if(day == 6)
    printf("Satday");
    printf(" ");
}

int calculateN(struct Date date) {
    int num;
    int fnFVal = fnF(date.year, date.month);
    int fnGval = fnG(date.month);
    num = (1461 * fnFVal) / 4 + (153 * fnGval) / 5 + date.day;
    return num;
}


int main()
{
    struct Date date;


    int day, month, year;
    printf("Enter Day : ");
    scanf("%d",&day);
    printf("Enter Month : ");
    scanf("%d",&month);
    printf("Enter Year : ");
    scanf("%d",&year);
    date.day = day;
    date.month = month;
    date.year = year;

    int N = calculateN(date);

    printDay(N);
    return 0;
}

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