题解 | 判断质数

#include <stdio.h>

int isqrt(int n) {
	if (n <= 1) {
		return n;
	}
	int x = n >> 1;
	int y = (x + (n / x)) >> 1;
	while (y < x) {
		x = y;
		y = (x + (n / x)) >> 1;
	}
	return x;
}

int main() {
	int n = 0;
	scanf("%d", &n);
    if (n == 1) {
        printf("No");
        return 0;
    }
	int qrt_n = isqrt(n);
	for (int i = 2;i <= qrt_n;i++) {
		if (n % i == 0) {
			printf("No");
			return 0;
		}
	}
	
	printf("Yes");
	return 0;
}