fast way to check if a number is prime C++
Check if a Number is Prime in C++
To check if a number is prime in C++, follow these steps:
Step 1: Start with the Number and Check for Base Cases
bool isPrime(int n) {
if (n <= 1) {
return false;
}
if (n <= 3) {
return true;
}
if (n % 2 == 0 || n % 3 == 0) {
return false;
}
// Starting from 5, check for prime
}
Step 2: Loop to Check for Prime
for (int i = 5; i * i <= n; i = i + 6) {
if (n % i == 0 || n % (i + 2) == 0) {
return false;
}
}
return true;
In this method, we check if the number is less than or equal to 1 and handle the base cases. Then, we start a loop from 5 and check if the number is divisible by i
or i+2
. If it is, we return false
; otherwise, the number is prime and we return true
.