In this HackerRank Prime Dates problem solution, the task is to debug the existing code to successfully execute all provided test files.

Given two dates each in the format dd-mm-yyyy, you have to find the number of lucky dates between them (inclusive). To see if a date is lucky,

Firstly, sequentially concatinate the date, month and year, into a new integer x erasing the leading zeroes.

Now if x is divisible by either 4 or 7, then we call the date a lucky date.

For example, let's take the date "02-08-2024". After concatinating the day, month and year, we get  x= 2082024. As x is divisible by 4 so the date "02-08-2024" is called a lucky date.

Debug the given function findPrimeDates and/or other lines of code, to find the correct lucky dates from the given input.

HackerRank Prime Dates problem solution



Problem solution in Python.

def updateLeapYear(year):
    if year % 400 == 0:
        month[2] = 29
    elif year % 100 == 0:
        month[2] = 28
    elif year % 4 == 0:
        month[2] = 29
    else:
        month[2] = 28

def findPrimeDates(d1, m1, y1, d2, m2, y2):
    storeMonth()
    result = 0

    while(True):
        x = d1
        x = x * 100 + m1
        x = x * 10000 + y1
        if x % 4 == 0 or x % 7 == 0:
            result = result + 1
        if d1 == d2 and m1 == m2 and y1 == y2:
            break
        updateLeapYear(y1)
        d1 = d1 + 1
        if d1 > month[m1]:
            m1 = m1 + 1
            d1 = 1
            if m1 > 12:
                y1 =  y1 + 1
                m1 = 1
    return result;

Problem solution in Java.

import java.util.*;
import java.lang.*;
import java.io.*;
import java.math.*;

public class Main {
    
    public static int month[];
    
    public static void main (String[] args) throws java.lang.Exception {
        Scanner in  = new Scanner(System.in);

        month = new int[15];

        String s = in.nextLine();

        StringTokenizer str = new StringTokenizer(s, "- ");

        int d1 = Integer.parseInt(str.nextToken());
        int m1 = Integer.parseInt(str.nextToken());
        int y1 = Integer.parseInt(str.nextToken());
        int d2 = Integer.parseInt(str.nextToken());
        int m2 = Integer.parseInt(str.nextToken());
        int y2 = Integer.parseInt(str.nextToken());
      
        int result = findPrimeDates(d1, m1, y1, d2, m2, y2);
        System.out.println(result);
   }

    public static void updateLeapYear(int year) {
        if(year % 400 == 0) {
            month[2] = 29;
        } else if(year % 100 == 0) {
            month[2] = 28;
        } else if(year % 4 == 0) {
            month[2] = 29;
        } else {
            month[2] = 28;
        }
    }
    
    public static void storeMonth() {
        month[1] = 31;
        month[2] = 28;
        month[3] = 31;
        month[4] = 30;
        month[5] = 31;
        month[6] = 30;
        month[7] = 31;
        month[8] = 31;
        month[9] = 30;
        month[10] = 31;
        month[11] = 30;
        month[12] = 31;
    }
   
   public static int findPrimeDates(int d1, int m1, int y1, int d2, int m2, int y2) {
        storeMonth();
    
        int result = 0;
    
        while(true) {
            int x = d1;
            x = x * 100 + m1;
            x = x * 10000 + y1;
            if(x % 4 == 0 || x % 7 == 0) {
                result = result + 1;
            }
            if(d1 == d2 && m1 == m2 && y1 == y2) {
                break;
            }
            updateLeapYear(y1);
            d1 = d1 + 1;
            if(d1 > month[m1]) {
                m1 = m1 + 1;
                d1 = 1;
                if(m1 > 12) {
                    y1 =  y1 + 1;
                    m1 = 1;
                }
            }
        }
        return result;
    }
}


Problem solution in C++.

void updateLeapYear(int year) {
    if(year % 400 == 0) {
        month[2] = 29;
    } else if(year % 100 == 0) {
        month[2] = 28;                 
    } else if(year % 4 == 0) {
        month[2] = 29;
    } else {
        month[2] = 28;
    }
}

void storeMonth() {
    month[1] = 31;
    month[2] = 28;
    month[3] = 31;
    month[4] = 30;
    month[5] = 31;
    month[6] = 30;
    month[7] = 31;
    month[8] = 31;
    month[9] = 30;
    month[10] = 31;
    month[11] = 30;
    month[12] = 31;
}

int findLuckyDates(int d1, int m1, int y1, int d2, int m2, int y2) {
    storeMonth();

    int result = 0;

    while(true) {
        int x = d1;
        x = x * 100 + m1;
        x = x * 10000 + y1;
        if(x % 4 == 0 || x % 7 == 0) {
            result = result + 1;
        }
        if(d1 == d2 && m1 == m2 && y1 == y2) {
            break;
        }
        updateLeapYear(y1);
        d1 = d1 + 1;
        if(d1 > month[m1]) {
            m1 = m1 + 1;
            d1 = 1;
            if(m1 > 12) {
                y1 =  y1 + 1;
                m1 = 1;
            }
        }
    }
    return result;
}