Check Leap Year in C, C++, Java & Python – Code with Explanation & Examples in Short and Simple

   

C Program

/* C - Check Leap Year (short & working) */
#include <stdio.h>
int main() {
    int y; scanf("%d", &y);
    printf((y%400==0 || (y%4==0 && y%100!=0)) ? "Leap Year\n" : "Not Leap Year\n");
    return 0;
}

C Output

Input:
2000
Output:
Leap Year

C++ Program

// C++ - Check Leap Year (short & working)
#include <bits/stdc++.h>
using namespace std;
int main() {
    int y; cin >> y;
    cout << ((y%400==0 || (y%4==0 && y%100!=0)) ? "Leap Year" : "Not Leap Year") << '\n';
}

C++ Output

Input:
1900
Output:
Not Leap Year

JAVA Program

// Java - Check Leap Year (short & working)
import java.util.*;
public class Main {
  public static void main(String[] args) {
    Scanner s = new Scanner(System.in);
    int y = s.nextInt();
    System.out.println((y%400==0 || (y%4==0 && y%100!=0)) ? "Leap Year" : "Not Leap Year");
  }
}

JAVA Output

Input:
2024
Output:
Leap Year

Python Program

# Python - Check Leap Year (short & working)
y = int(input())
print("Leap Year" if (y%400==0 or (y%4==0 and y%100!=0)) else "Not Leap Year")

Python Output

Input:
2023
Output:
Not Leap Year

In-Depth Learning – Entire Concept in Paragraphs

Example

Consider the C version with input 2000. The rule stipulates a year is a leap year if it's divisible by 400, or if divisible by 4 but not 100. As 2000 is divisible by 400, it's a leap year. For 1900, while divisible by 4 and 100, it doesn't meet the "not divisible by 100 but divisible by 400" requirement and so isn't a leap year.

Real-Life Analogy

Consider planning a birthday for a person born on February 29. You only get to celebrate on the actual date if the year obeys the leap year rules — such as a club where the membership is extremely difficult: either you possess the premier "400 pass", or you possess the "4 pass" but must avoid the "100 ban" unless you also possess the "400 pass".

Learning Insights

This exercise instructs in multiple operator conditional logic, and how to group conditions with logical &&/and and ||/or. It's an example of the kind of real-world situation where knowing operator precedence is important, since mis-grouping conditions will make the logic fail. It's also an example of following strict rules in coding vs. simplifying the issue too much.

Why It Matters

Leap year calculation isn't merely theoretical — it pops up in real systems such as calendars, date pickers, scheduling software, astronomy programs, and billing cycles. To mess it up is to cause real-world bugs, such as erroneous expiry dates or lost events in software.

Interview Use Case

In interviews, the leap year is a rapid logic exercise to determine whether you can convert accurate conditions to neat code. The interviewer can extend it to handle date validation, library usage, or working with leap years in historical calendars (Julian vs Gregorian). They can occasionally request a leap year range finder or a leap year day count calculator.

Extensions and Optimization

Although this issue is already O(1), you can grow it with adding a function to test leap years in bulk, or incorporating it into date-handling classes. For historical accuracy, you may add both Julian and Gregorian rules with switching logic for dates before 1582.

How It Shows Up in Actual Projects

Most date libraries do leap year handling internally, but in low-level software, embedded systems, or custom date code, you might need to perform the check yourself. Banking systems, subscription systems, and booking systems for travel depend on the correctness of leap year detection for interest computation, billing periods, or ticket validity. 

Common Pitfalls

A common error is testing for divisibility by 4 alone, which applies to most years but not to century years such as 1900. Another is overlooking operator precedence and lack of parentheses, which alters the order of computation and provides erroneous results.

SEO-Optimized Paragraph

A C, C++, Java, or Python leap year program determines if a specified year satisfies the rule for a leap year: divisible by 400, or divisible by 4 but not by 100. Such simple but accurate logic is critical to date verification, calendar programs, and scheduling software. Knowing and implementing leap year tests assists developers in dealing with date issues of the real world, preventing elusive bugs in programs, and anticipating interview questions where proper condition handling is important. Efficient mastery of leap year logic solidifies programming fundamentals as well as real-world problem-solving skills.