Question

How to calculate the 1000st prime number in C

Answer 1

#include <math.h>
#include <stdio.h>
#include <stdbool.h>
 
bool isPrime(int n) {
    if (n == 0) return false;
    if (n == 1) return false;
 
    for (int i = 2; i <= sqrt(n); i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}
 
int main(void) {
    int i = 0;
    int prime = 2;
 
    while (i < 1000) {
        if (isPrime(prime)) {
            i++;
        }
        prime++;
    }
    
    printf("%d ", --prime);
}
 
 
 
 
/*
run:
 
7919
 
*/

 

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Answer 2

#include <math.h>
#include <stdio.h>
#include <stdbool.h>
 
bool isPrime(int n) {
    if (n == 0) return false;
    if (n == 1) return false;
 
    for (int i = 2; i <= sqrt(n); i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

int getTheNthPrimeNumber(int N) {
    int i = 0;
    int prime = 2;
 
    while (i < N) {
        if (isPrime(prime)) {
            i++;
        }
        prime++;
    }
    
    return --prime;
}
 
int main(void) {
    printf("%d ", getTheNthPrimeNumber(1000));
}
 
 
 
 
/*
run:
 
7919
 
*/

 

Cleaner teeth, healthier you!
Get The Secret to a Bright and Healthy Smile