Print all palindrome dates between the given years

• Difficulty Level : Basic
• Last Updated : 16 Dec, 2019

Given two years Y1 and Y2 where 103 ≤ Y1 ≤ Y2 ≤ 106, the task is to find and print all the dates which are palindromes between the given years.

Examples:

Input: Y1 = 2001, Y2 = 2005
Output:
10022001
20022002

Input: Y1 = 5000, Y2 = 5010
Output:
10055001
20055002
30055003
01055010

Approach: Since the first four digits (i.e. the day and the month) have to be the reverse of the last four digits (the year) in order for the date to be a palindrome. So, every year will have at most one palindrome date. In order to find the dates, for every year reverse the year number and check whether the date formed is valid or not. If it is valid then print it.

Below is the implementation of the above approach:

C++

 // C++ implementation of the approach#include using namespace std;  const int MAX_VALID_YR = 9999;const int MIN_VALID_YR = 1800;  // Returns true if// given year is validbool isLeap(int year){    // Return true if year    // is a multiple pf 4 and    // not multiple of 100.    // OR year is multiple of 400.    return (((year % 4 == 0)             && (year % 100 != 0))            || (year % 400 == 0));}  // Returns true if given// year is valid or not.bool isValidDate(int d, int m, int y){    // If year, month and day    // are not in given range    if (y > MAX_VALID_YR || y < MIN_VALID_YR)        return false;    if (m < 1 || m > 12)        return false;    if (d < 1 || d > 31)        return false;      // Handle February month    // with leap year    if (m == 2) {        if (isLeap(y))            return (d <= 29);        else            return (d <= 28);    }      // Months of April, June,    // Sept and Nov must have    // number of days less than    // or equal to 30.    if (m == 4 || m == 6 || m == 9 || m == 11)        return (d <= 30);      return true;}  // Function to print the palindrome// dates between the given yearsvoid printPalindromeDates(int y1, int y2){      // For every year    for (int year = y1; year <= y2; year++) {          // Current year as a string        string str = to_string(year);          // To store the reverse of year        string rev = str;        reverse(rev.begin(), rev.end());          // Get the day and the month        int day = stoi(rev.substr(0, 2));        int month = stoi(rev.substr(2, 2));          // If the current palindrome date is valid        if (isValidDate(day, month, year)) {            cout << rev << str << endl;        }    }}  // Driver codeint main(){    int y1 = 2001, y2 = 2005;      printPalindromeDates(y1, y2);      return 0;}

Java

 // Java implementation of the approachclass GFG{  static int MAX_VALID_YR = 9999;static int MIN_VALID_YR = 1800;  // Returns true if// given year is validstatic boolean isLeap(int year){    // Return true if year    // is a multiple pf 4 and    // not multiple of 100.    // OR year is multiple of 400.    return (((year % 4 == 0)            && (year % 100 != 0))            || (year % 400 == 0));}  // Returns true if given// year is valid or not.static boolean isValidDate(int d, int m, int y){    // If year, month and day    // are not in given range    if (y > MAX_VALID_YR || y < MIN_VALID_YR)        return false;    if (m < 1 || m > 12)        return false;    if (d < 1 || d > 31)        return false;      // Handle February month    // with leap year    if (m == 2)     {        if (isLeap(y))            return (d <= 29);        else            return (d <= 28);    }      // Months of April, June,    // Sept and Nov must have    // number of days less than    // or equal to 30.    if (m == 4 || m == 6 || m == 9 || m == 11)        return (d <= 30);      return true;}  // Function to print the palindrome// dates between the given yearsstatic void printPalindromeDates(int y1, int y2){      // For every year    for (int year = y1; year <= y2; year++)    {          // Current year as a String        String str = String.valueOf(year);          // To store the reverse of year        String rev = str;        rev = reverse(rev);          // Get the day and the month        int day = Integer.parseInt(rev.substring(0, 2));        int month = Integer.parseInt(rev.substring(2, 2 + 2));          // If the current palindrome date is valid        if (isValidDate(day, month, year))        {            System.out.print(rev + str +"\n");        }    }}static String reverse(String input) {        char[] a = input.toCharArray();        int l, r = a.length - 1;        for (l = 0; l < r; l++, r--)         {            char temp = a[l];            a[l] = a[r];            a[r] = temp;        }        return String.valueOf(a);    }      // Driver codepublic static void main(String[] args){    int y1 = 2001, y2 = 2005;      printPalindromeDates(y1, y2);  }}  // This code is contributed by PrinciRaj1992

Python 3

 # Python 3 implementation of the approachMAX_VALID_YR = 9999MIN_VALID_YR = 1800  # Returns true if given year is validdef isLeap(year):          # Return true if year    # is a multiple pf 4 and    # not multiple of 100.    # OR year is multiple of 400.    return (((year % 4 == 0) and              (year % 100 != 0)) or              (year % 400 == 0))  # Returns true if given# year is valid or not.def isValidDate(d, m, y):          # If year, month and day    # are not in given range    if (y > MAX_VALID_YR or y < MIN_VALID_YR):        return False    if (m < 1 or m > 12):        return False    if (d < 1 or d > 31):        return False      # Handle February month    # with leap year    if (m == 2):        if (isLeap(y)):            return (d <= 29)        else:            return (d <= 28)      # Months of April, June,    # Sept and Nov must have    # number of days less than    # or equal to 30.    if (m == 4 or m == 6 or         m == 9 or m == 11):        return (d <= 30)      return True  # Function to print the palindrome# dates between the given yearsdef printPalindromeDates(y1, y2):          # For every year    for year in range(y1, y2 + 1, 1):                  # Current year as a string        str1 = str(year)          # To store the reverse of year        rev = str1        rev = rev[::-1]          # Get the day and the month        day = int(rev[0 : 2])        month = int(rev[2 : 4])          # If the current palindrome date is valid        rev += str1        if (isValidDate(day, month, year)):            print(rev)  # Driver codeif __name__ == '__main__':    y1 = 2001    y2 = 2005      printPalindromeDates(y1, y2)      # This code is contributed by Surendra_Gangwar

C#

 // C# implementation of the approachusing System;  class GFG{static int MAX_VALID_YR = 9999;static int MIN_VALID_YR = 1800;  // Returns true if// given year is validstatic bool isLeap(int year){    // Return true if year    // is a multiple pf 4 and    // not multiple of 100.    // OR year is multiple of 400.    return (((year % 4 == 0) &&              (year % 100 != 0)) ||              (year % 400 == 0));}  // Returns true if given// year is valid or not.static bool isValidDate(int d, int m, int y){    // If year, month and day    // are not in given range    if (y > MAX_VALID_YR || y < MIN_VALID_YR)        return false;    if (m < 1 || m > 12)        return false;    if (d < 1 || d > 31)        return false;      // Handle February month    // with leap year    if (m == 2)     {        if (isLeap(y))            return (d <= 29);        else            return (d <= 28);    }      // Months of April, June,    // Sept and Nov must have    // number of days less than    // or equal to 30.    if (m == 4 || m == 6 || m == 9 || m == 11)        return (d <= 30);      return true;}  // Function to print the palindrome// dates between the given yearsstatic void printPalindromeDates(int y1, int y2){      // For every year    for (int year = y1; year <= y2; year++)    {          // Current year as a String        String str = String.Join("", year);          // To store the reverse of year        String rev = str;        rev = reverse(rev);          // Get the day and the month        int day = Int32.Parse(rev.Substring(0, 2));        int month = Int32.Parse(rev.Substring(2, 2));          // If the current palindrome date is valid        if (isValidDate(day, month, year))        {            Console.Write(rev + str +"\n");        }    }}  static String reverse(String input) {    char[] a = input.ToCharArray();    int l, r = a.Length - 1;    for (l = 0; l < r; l++, r--)     {        char temp = a[l];        a[l] = a[r];        a[r] = temp;    }    return String.Join("", a);}      // Driver codepublic static void Main(String[] args){    int y1 = 2001, y2 = 2005;      printPalindromeDates(y1, y2);}}  // This code is contributed by 29AjayKumar
Output:
10022001
20022002

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