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Date after N days

ISC 2009 Computer Science Practical, Question 1 · Date programs

This question was set again in ISC 2019 as Question 1. See that page for the later version.

The question

Design a program to accept a day number (between 1 and 366), year (in 4 digits) from the user to generate and display the corresponding date.

Also, accept ‘N’ (1 <= N <= 100) from the user to compute and display the future date corresponding to ‘N’ days after the generated date.

Display an error message if the value of the day number, year and N are not within the limit or not according to the condition specified.

Test your program with the following data and some random data:

Example 1

INPUT:
DAY NUMBER:             233
YEAR:                     2008
DATE AFTER (N DAYS):     17

OUTPUT:
DATE:                     20 TH AUGUST, 2008
DATE AFTER 17 DAYS:     6 TH SEPTEMBER, 2008

Example 2

INPUT:
DAY NUMBER:             360
YEAR:                     2008
DATE AFTER (N DAYS):     45

OUTPUT:
DATE:                     20 TH AUGUST, 2008
DATE AFTER 45 DAYS:     8 TH FEBRUARY, 2009

Question: ISC 2009 Computer Science Paper 2 (Practical), Question 1, set by the Council for the Indian School Certificate Examinations (CISCE). Solution and video: Vinay Singh.

Java solution

ISC2009Q1.java Download GitHub

import java.util.*;

class Date {
    private int day, month, year;

    public Date(int day, int month, int year) {
        this.day = day;
        this.month = month;
        this.year = year;
    }

    public String toString() {
        String suffix[] = { "TH", "ST", "ND", "RD", "TH", "TH", "TH", "TH", "TH", "TH" };
        String monthName[] = { "JANUARY", "FEBRUARY", "MARCH", "APRIL", "MAY", "JUNE", "JULY", "AUGUST", "SEPTEMBER",
                "OCTOBER", "NOVEMBER", "DECEMBER" };
        String finalSuffix;
        if (day > 9 && day < 21)
            finalSuffix = "TH";
        else
            finalSuffix = suffix[day % 10];
        return day + " " + finalSuffix + " " + monthName[month - 1] + ", " + year;
    }
}

class ISC2009Q1 {
    static int dayNumber, year, N;

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.println("INPUT");
        System.out.print("DAY NUMBER:\t\t");
        dayNumber = in.nextInt();
        System.out.print("YEAR:\t\t\t");
        year = in.nextInt();
        System.out.print("DATE AFTER (N DAYS):\t");
        N = in.nextInt();

        System.out.println("OUTPUT");
        if (dayNumber < 1 || dayNumber > 366) {
            System.out.println("DAY NUMBER OUT OF RANGE.");
        } else if (year < 1000 || year > 9999) {
            System.out.println("YEAR OUT OF RANGE.");
        } else if (N < 1 || N > 100) {
            System.out.println("DATE AFTER (N DAYS) OUT OF RANGE.");
        } else {
            Date dt = dateFromDayNumber(dayNumber, year);
            System.out.println("DATE:\t\t\t" + dt);
            int nextDayNumber = dayNumber + N, nextYear;
            if (nextDayNumber > 365) {
                nextYear = year + 1;
            } else {
                nextYear = year;
            }
            if (isLeap(year)) {
                nextDayNumber = nextDayNumber % 366;
            } else {
                nextDayNumber = nextDayNumber % 365;
            }
            Date dateAfterNDays = dateFromDayNumber(nextDayNumber, nextYear);
            System.out.println("DATE AFTER " + N + " DAYS:\t" + dateAfterNDays);
        }
        in.close();
    }

    private static Date dateFromDayNumber(int dayNumber, int year) {
        int month[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        if (isLeap(year))
            month[1] = 29;
        int monthNumber;
        for (monthNumber = 0; monthNumber < month.length; monthNumber++) {
            if (dayNumber <= month[monthNumber])
                break;
            dayNumber -= month[monthNumber];
        }
        return new Date(dayNumber, monthNumber + 1, year);
    }

    public static boolean isLeap(int year) {
        // int divisor;
        // if(year%100==0) divisor=400;
        // else divisor=4;
        // return year%divisor==0;
        return year % (year % 100 == 0 ? 400 : 4) == 0;
    }
}

Date after N days

The question

Java solution

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