#### Concepts Used:

Mathematics

#### Difficulty Level:

Hard

#### Problem Statement (Simplified):

For given three numbers

`r`

,`p`

,`q`

. We have to find the total number of values divisible by`r`

in a range [`p`

,`q`

]. (Both Inclusive).

**See original problem statement here**

#### Test Case:

```
Input:
1
3 -10 30
Output:
14
Explaination:
There are total
````14`

numbers divisible by `3`

in range [-10,30], that are `[-9,-6,-3,0,3,6,9,12,15,18,21,24,27,30]`

#### Solving Approach :

*Bruteforce Approach:*

1) We can start a loop from

`p`

to`q`

, and then check if the current value is divisible by`r`

or not, if yes, we increase the counter by 1.

2) After all numbers in a given range are iterated, we print the count.

3) This approach takes`O(q-p)`

time complexity for a given range. But this approach is inefficient for larger ranges and a larger number of queries. So we go through the best sites to learn programming languages and move to a more efficient approach.

*Efficient Approach:*

1) We can find that by dividing

`p`

and`q`

by`r`

.

2)`q/r`

gives total number of values divisible by`r`

in range [`1,q`

] ( or [`q,-1`

] if`q`

is negative).

3)`p/r`

gives total number of values divisible by`r`

in range [`1,p`

] ( or [`p,-1`

] if`p`

is negative).

4) We can get our answer on subtracting number of values found in range [`1,p`

] ( or [`p,-1`

] ) from number of values found in range [`1,q`

] ( or [`q,-1`

] ).

5) An extra value should also be considered if following conditions are satisfied:

a) If range contains`0`

, we would add an additional 1, as`0`

is divisible by`r`

but is not counted by above method.

b) If`p`

and`q`

both values are positive and`p`

is divisible by`r`

.

c) If`p`

and`q`

both values are negative and`q`

is divisible by`r`

.

#### Example:

We’ll take an example for different range cases :

Case 1: Negative to NegativeAssuming range as [-12,-2] and

`r=3`

, here gives`-4`

and gives`0`

, hence there are`4`

numbers between range`[-12,-1]`

i.e.`[-12,-9,-6,-3]`

. Also there is no number in range`[-2, -1]`

, hence there are total`4`

numbers which are divisible by ‘r’ in range`[-12,-2]`

.

If range near to 0 is divisible byNOTE:`r`

, we add additional 1 to answer, that it is counted in both ranges i.e. [p,-1] and [q,-1] and on substraction, it is discarded, so we add an extra 1 in answer for it.

Case 2: Positive to PositiveAssuming range as [2,12] and

`r=3`

, here gives`0`

and gives`4`

, hence there are`4`

numbers between range`[1,12]`

i.e.`[3,6,9,12]`

. Also there is no number in range`[1,2]`

, hence there are total`4`

numbers which are divisible by ‘r’ in range`[2, 12]`

.

If range near to 0 is divisible byNOTE:`r`

, we add additional 1 to answer, that it is counted in both ranges i.e. [1,p] and [1,q] and on substraction, it is discarded, so we add an extra 1 in answer for it.

Case 3: Negative to PositiveAssuming range as [-12,12] and

`r=3`

, here gives`-4`

and gives`4`

, hence there are`4`

numbers between range`[-12, 1]`

i.e.`[3,6,9,12]`

. Also there are`4`

numbers in range`[1,12]`

. Also,`0`

is also divisible by`3`

, so it will be included as well as. Hence there are total`9`

numbers which are divisible by ‘r’ in range`[-12, 12]`

.

#### Solutions:

[TABS_R id=809]

[forminator_quiz id=”819″]