素数的判断与素数表的获取

bool isprime(int n) {
    if (n <= 0)
        return false;
    int sqr = (int)sqrt(1.0 * n);
    for (int i = 2; i <= sqr; i++) {
        if (n % i == 0)
            return false;
    }
    return true;
}

const int maxn = 101;
int prime[maxn], pnum = 0;
bool p[maxn] = { false };
void findPrime() {
    for (int i = 1; i < maxn; i++) {
        if (isprime(i)) {
            prime[pnum++] = i;
            p[i] = true;
        }
    }
}

const int maxn = 101;
int prime[maxn], pnum = 0;
bool p[maxn] = { false };
void findPrime() {
    for (int i = 2; i < maxn; i++) {
        if (!p[i]) {
            prime[pnum++] = i;
            for (int j = i + i; j < maxn; j++) {
                p[i] = true;
            }
        }
    }
}