September 16, 2021, Learn eTutorial

764

**A year that has 366 days (with an extra day in February 29 days, usually 28 days) is called a LEAP YEAR**. A leap year is coming after 3 normal years ie., the 4th year after a leap year will be the other one. Here, we are explaining how to check whether the given year is a leap or not.

- If a year given is divisible by 4 without any remainder means it's a leap year, otherwise not.
- If the given year is a century (years ending with 00) then it should also be divisible by 400 otherwise, it's not a leap year

Leap year check can be implemented very simply using `nested if .. else condition`

in R programming. First, we will ask the user to enter a year for leap year checking. R provides `readline()`

function for taking the user's input by prompting an appropriate message to the user for data using '`prompt`

'.

Here the user is asked to enter a year, data will be stored to a variable named **year**. Then, check the given **year** can be divided** **by 4, If the remainder is zero it is a leap year otherwise not a leap year. Also, check the given year is a century (eg., 2000) dividing the **year** by 100 without any remainder; then divide the **year** by 400 and check whether the remainder is 0, if that condition is also satisfied then it is a leap year, and if not means it's a normal year.

Let's understand with some examples,

Consider the year 2004, it is completely divided by 4 and thus it is a leap year. If we take 2005 it is not fully divided by 4 and thus it's not a leap year.

Now check examples of the century years, we should satisfy an extra condition for century ie., for a century being leap year we should also divide it by 400 and check any remainder left. Consider the year 2000, it can be divided by 4 and let's confirm it is a century as dividing 2000 by 100 and then to check for leap year divide by 400. Here 2000 is a century and a leap year, but if we take 1900 it will satisfy the first 2 conditions but won't divide by 400 and thus it's not a leap year.

**STEP 1**: Read a year prompting appropriate messages to the user using `readline()`

into variable **year**

**STEP 2**: First look for a century, use nested `if condition`

to check **year** is exactly divisible by **4,100,400** and gives a remainder of 0;

- If yes
`print`

The year is a leap year - else
`print`

The year is not a leap year

**STEP 3**: If a **year** is divisible by 4 but not by 100 means year is not a century then `print`

The year is a leap year

**STEP 4**: If a **year** is not divisible by 4 then `print`

The year is not a leap year

` ````
year = as.integer(readline(prompt="Enter a year: "))
if((year %% 4) == 0) {
if((year %% 100) == 0) {
if((year %% 400) == 0) {
print(paste(year,"is a leap year"))
} else {
print(paste(year,"is not a leap year"))
}
} else {
print(paste(year,"is a leap year"))
}
} else {
print(paste(year,"is not a leap year"))
}
```

Enter a year: 2011 [1] "2011 is not a leap year" Enter a year: 2004 [1] "2004 is a leap year"