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C++ program to find numbers with K odd divisors in a given range
In this problem, we are given three integer values, L, R, and k. Our task is to find numbers with K divisors in a given range. We will be finding the count of numbers in the range [L, R] that have exactly k divisors. We will be counting the 1 and the number itself as a divisor.
Let’s take an example to understand the problem,
Input
a = 3, b = 10, k = 4
Output
2
Explanation
Numbers with exactly 3 divisors within the range 3 to 10 are 6 : divisors = 1, 2, 3, 6 8 : divisors = 1, 2, 4, 8
Solution Approach
A simple solution to the problem is by counting the k divisors.. So, we will count the number of divisors for all numbers in the range. And if the count of divisors in k, we will add 1 to the number count.
Program to illustrate the working of our solution,
Example
#include<bits/stdc++.h> using namespace std; int countDivisors(int n) { int divisors = 0; for (int i=1; i<=sqrt(n)+1; i++) { if (n%i==0) { divisors++; if (n/i != i) divisors ++; } } return divisors; } int countNumberKDivisors(int a,int b,int k) { int numberCount = 0; for (int i=a; i<=b; i++) { if (countDivisors(i) == k) numberCount++; } return numberCount; } int main() { int a = 3, b = 10, k = 4; cout<<"The count of numbers with "<<k<<" divisors is "<<countNumberKDivisors(a, b, k); return 0; }
Output
The count of numbers with 4 divisors is 2
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