C Programming Solved Problems Let us C Yashwant Kanitkar Chapter 3 Question (d)

Q: (d) According to the Gregorian calendar, it was Monday on the date 01/01/01. If any year is input through the keyboard write a program to find out what is the day on 1st January of this year.

 #include <stdio.h>

int isLeapYear(int year)

{

    if ((year%4==0&&year%100!=0)||(year%400==0))

        return 1;

    else

        return 0;

}

int main()

{

    int year,dayIndex=0;//0 for monday

    int daysInYear;

    char *days[]={"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"};

    printf("Enter the year: ");

    scanf("%d", &year);

    for (int y = 1; y < year; y++)

    {

        if (isLeapYear(y))

            dayIndex+=366;//if leap year add 1 extra day

        else

            dayIndex+=365;

    }

    dayIndex=dayIndex%7;//remainder for day number

    printf("1st January of year %d is a %s.\n", year, days[dayIndex]);

    return 0;

}

Download Source Code