Question

Write an algorithm to display the first 10 multiples of 7.​

Answer 1

An efficient solution can solve the above problem in O(1) time. The idea is to count multiples of 3 and add multiples of 7, then subtract multiples of 21 because these are counted twice.

count = n/3 + n/7 - n/21

// A better C++ program to find count of all

// numbers that multiples

#include<iostream>

using namespace std;

// Returns count of all numbers smaller than

// or equal to n and multples of 3 or 7 or both

int countMultiples(int n)

{

return n/3 + n/7 -n/21;

}

// Driver code

int main()

{

cout << "Count = " << countMultiples(25);

}