Primality C++ Test Using a Basic Concept of Number Theory
Primality testing is some sort of exciting stuff for a beginner in coding. There are various techniques for doing this. Following code is written by me that used the following fact that -: "N is a composite number if it has at least one non-trivial divisor d, such that d is less than or equal to sqrt(N)". Proof of the fact is simple and can be proved using contradiction(Hint -; N is composite. What if all the non-trivial divisors are greater than sqrt(N)? ). Direct link -: http://cpp.sh/7sng3 // To detect whether a number is prime or not. // Written by Sushant #include <iostream> #include<cmath> using namespace std; int main() { int p,q,i(0),d(0); cout<<"Enter the number -: \n"; cin>>p; // enter the prime q=int(sqrt(p)); // storing the integer part of square root for(i=2; i <= q;i++) { // using the fact that if x is a composite number then it must have a non-tr