[Codility] Lesson5 - CountDiv

Task discription

Write a function:

class Solution { public int solution(int A, int B, int K); }

that, given three integers A, B and K, returns the number of integers within the range [A..B] that are divisible by K, i.e.:

{ i : A ≤ i ≤ B, i mod K = 0 }

For example, for A = 6, B = 11 and K = 2, your function should return 3, because there are three numbers divisible by 2 within the range [6..11], namely 6, 8 and 10.
Write an efficient algorithm for the following assumptions:

A and B are integers within the range [0..2,000,000,000];

K is an integer within the range [1..2,000,000,000];

A ≤ B.

Source code

#include <iostream>
#include <algorithm>

using namespace std;

int solution(int A, int B, int K) {
    int ans = B/K - A/K;
    if(A%K == 0) ans++;
    return ans;
}