Leap Year Checker - Problem

Given a year, determine whether it is a leap year or not.

A leap year is a year that is divisible by 4, except for years that are divisible by 100, unless they are also divisible by 400.

Rules for leap years:

If the year is divisible by 4, it might be a leap year
If the year is divisible by 100, it is not a leap year
If the year is divisible by 400, it is a leap year

Return true if the year is a leap year, false otherwise.

Input & Output

Example 1 — Leap Year (Divisible by 400)

$ Input: year = 2000

› Output: true

💡 Note: 2000 is divisible by 400, so it's a leap year despite being divisible by 100

Example 2 — Not Leap Year (Century Year)

$ Input: year = 1900

› Output: false

💡 Note: 1900 is divisible by 100 but not by 400, so it's not a leap year

Example 3 — Leap Year (Regular)

$ Input: year = 2024

› Output: true

💡 Note: 2024 is divisible by 4 and not by 100, so it's a leap year

Constraints

1 ≤ year ≤ 3000
Year is a positive integer

Visualization

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Asked in

a Amazon 25 M Microsoft 18

The key insight is understanding the three-tier leap year rule: divisible by 4 (base rule), except if divisible by 100 (exception), unless also divisible by 400 (exception to the exception). Best approach combines all conditions into a single boolean expression: year % 4 == 0 && (year % 100 != 0 || year % 400 == 0). Time: O(1), Space: O(1)

Common Approaches

✓ Multiple Separate Checks

⏱️ Time: O(1) Space: O(1)

Check divisibility by 4, 100, and 400 using separate conditional statements, handling each case independently without combining the logic efficiently.

Single Combined Expression

⏱️ Time: O(1) Space: O(1)

Use logical AND and OR operators to combine all three leap year conditions into a single, concise boolean expression that evaluates efficiently.

Multiple Separate Checks — Algorithm Steps

Check if year is divisible by 400 - return true
Check if year is divisible by 100 - return false
Check if year is divisible by 4 - return true
Otherwise return false

Visualization

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Step-by-Step Walkthrough

Check 400

If divisible by 400, return true

Check 100

If divisible by 100, return false

Check 4

If divisible by 4, return true, else false

Code -

solution.c — C

#include <stdio.h>

int solution(int year) {
    if (year % 400 == 0) {
        return 1;
    }
    if (year % 100 == 0) {
        return 0;
    }
    if (year % 4 == 0) {
        return 1;
    }
    return 0;
}

int main() {
    int year;
    scanf("%d", &year);
    int result = solution(year);
    printf(result ? "true\n" : "false\n");
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Three modulo operations at most, constant time

✓ Linear Growth

Space Complexity

O(1)

No extra variables needed, only constant space

✓ Linear Space

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Leap Year Checker - Problem

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Multiple Separate Checks — Algorithm Steps

Visualization

Code -

Time & Space Complexity

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