素数

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[C++] 纯文本查看 复制代码

bool isPrime(int n) {
    if (n <= 1) {
        return false;
    }
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

int countPrimes(int n) {
    int count = 0;
    for (int i = 2; i <= n; i++) {
        if (isPrime(i)) {
            count++;
        }
    }
    return count;
}

int sumPrimes(int n) {
    int sum = 0;
    for (int i = 2; i <= n; i++) {
        if (isPrime(i)) {
            sum += i;
        }
    }
    return sum;
}

int main() {
    int x;
    cin >> x;
    cout << countPrimes(x) << " " << sumPrimes(x) << endl;
    return 0;
}

admin

[C++] 纯文本查看 复制代码

#include<iostream>
#include<cmath>
using namespace std;
bool judge(int x);
int main() {
    int n;
    int i;
    int sum = 0;
    cin >> n;
    for(i = 2;i <= n;i++)
        if(judge(i))//若是素数
            sum++;//累加素数个数
    cout << sum << endl;
    return 0;
}
bool judge(int x)//判断素数
{
    int i = 2;
    while(i <= floor(sqrt(x)) && (x % i) != 0)
        i++;
    if(i > floor(sqrt(x)))
        return true;
    return false;
}

admin

[C++] 纯文本查看 复制代码

#include <iostream>
using namespace std;
bool is_prime[100];

int main() {
    for (int i = 2; i < 100; i++) {
        is_prime[i] = true;
    }
    for (int i = 2; i * i < 100; i++) {
        if (is_prime[i]) {
            for (int j = i * i; j < 100; j += i) {
                is_prime[j] = false;
            }
        }
    }
for (int i = 2; i < 100; i++) {
    if (is_prime[i]) {
        cout << i << endl;
    }
}

    return 0;
}