Print all palindrome dates between the given years

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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 <bits/stdc++.h>
using namespace std;
 
const int MAX_VALID_YR = 9999;
const int MIN_VALID_YR = 1800;
 
// Returns true if
// given year is valid
bool isLeap(int year)
{
    // Return true if year
    // is a multiple of 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 years
void 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 code
int main()
{
    int y1 = 2001, y2 = 2005;
 
    printPalindromeDates(y1, y2);
 
    return 0;
}

Java

// Java implementation of the approach
class GFG
{
 
static int MAX_VALID_YR = 9999;
static int MIN_VALID_YR = 1800;
 
// Returns true if
// given year is valid
static boolean isLeap(int year)
{
    // Return true if year
    // is a multiple of 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 years
static 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 code
public 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 approach
MAX_VALID_YR = 9999
MIN_VALID_YR = 1800
 
# Returns true if given year is valid
def isLeap(year):
     
    # Return true if year
    # is a multiple of 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 years
def 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 code
if __name__ == '__main__':
    y1 = 2001
    y2 = 2005
 
    printPalindromeDates(y1, y2)
     
# This code is contributed by Surendra_Gangwar

C#

// C# implementation of the approach
using System;
 
class GFG
{
static int MAX_VALID_YR = 9999;
static int MIN_VALID_YR = 1800;
 
// Returns true if
// given year is valid
static bool isLeap(int year)
{
    // Return true if year
    // is a multiple of 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 years
static 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 code
public static void Main(String[] args)
{
    int y1 = 2001, y2 = 2005;
 
    printPalindromeDates(y1, y2);
}
}
 
// This code is contributed by 29AjayKumar

Javascript

// JS implementation of the approach
let MAX_VALID_YR = 9999;
let MIN_VALID_YR = 1800;
 
// Returns true if
// given year is valid
function isLeap(year)
{
    // Return true if year
    // is a multiple of 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.
function isValidDate(d, m, 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 years
function printPalindromeDates(y1, y2)
{
 
    // For every year
    for (let year = y1; year <= y2; year++) {
 
        // Current year as a string
        let str = "" + year;
 
        // To store the reverse of year
        let rev = str.split("").reverse().join("");
 
 
        // Get the day and the month
        let day = parseInt(rev.substr(0, 2));
        let month = parseInt(rev.substr(2, 2));
 
        // If the current palindrome date is valid
        if (isValidDate(day, month, year)) {
            console.log(rev + str);
        }
    }
}
 
// Driver code
let y1 = 2001, y2 = 2005;
printPalindromeDates(y1, y2);
 
// This code is contributed by phasing17

Output:

10022001
20022002

Time Complexity: O(y2 – y1)

Auxiliary Space: O(1)

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