Write a function to find the count of the number of prime numbers in a specified range. The starting and ending number of the range will
be provided as input parameters to the function.
Answers
Answer:
C++ program to find the prime numbers
Explanation:
// C++ program to find the prime numbers
// between a given interval
#include <bits/stdc++.h>
using namespace std;
int main()
{
// Declare the variables
int a, b, i, j;
// Ask user to enter lower value of interval please not
// interval < 0 cannot be prime numbers
cout << "Enter lower bound of the interval: ";
cin >> a; // Take input
// Ask user to enter upper value of interval
cout << "\nEnter upper bound of the interval: ";
cin >> b; // Take input
// Print display message
cout << "\nPrime numbers between " << a << " and " << b
<< " are: ";
// Explicitly handling the cases when a is less than 2
// since 0 and 1 are not prime numbers
if (a <= 2) {
a = 2;
if (b >= 2) {
cout << a << " ";
a++;
}
}
// MAKING SURE THAT a IS ODD BEFORE WE BEGIN
// THE LOOP
if (a % 2 == 0)
a++;
// NOTE : WE TRAVERSE THROUGH ODD NUMBERS ONLY
for (i = a; i <= b; i = i + 2) {
// flag variable to tell
// if i is prime or not
bool flag = 1;
// WE TRAVERSE TILL SQUARE ROOT OF j only.
// (LARGEST POSSIBLE VALUE OF A PRIME FACTOR)
for (j = 2; j * j <= i; ++j) {
if (i % j == 0) {
flag = 0;
break;
}
}
// flag = 1 means i is prime
// and flag = 0 means i is not prime
if (flag == 1)
cout << i << " ";
}
return 0;
}