C++学习 第三章 循环语句

第三章 循环语句

P708 偶数

#include<iostream>

using namespace std;

int main(){
    
    for(int i=2;i<=100;i++){
        if(i%2==0){
            cout<<i<<endl;
        }
    }
}

P712 正数

#include<iostream>
using namespace std;

int main(){
    
    int cnt = 0;
    for(int i=0;i<6;i++){
        double x;
        cin>>x;
        if(x>0) cnt++;
    }
    
    cout << cnt <<" positive numbers"<<endl;
    
    return 0;
}

P717 斐波那契数列

#include<iostream>

using namespace std;

int main(){
    
    int n;
    cin >> n;
    int a= 0;
    int b = 1;
    for (int i = 0; i < n; i ++ )
    {
        cout << a << ' ';
        int c = a + b;
        a = b;
        b = c;
    }
    cout<<endl;
    
    return 0;
    
}

P726 质数

#include <cstdio>
#include <iostream>

using namespace std;

int main()
{
    int n;
    cin >> n;
    while (n -- )
    {
        int p;
        cin >> p;

        bool is_prime = true;
        for (int i = 2; i * i <= p; i ++ )
            if (p % i == 0)
            {
                is_prime = false;
                break;
            }

        if (is_prime) printf("%d is prime\n", p);
        else printf("%d is not prime\n", p);
    }

    return 0;
}

P725 完全数

#include <cstdio>
#include <iostream>

using namespace std;

int main()
{
    int n;
    cin >> n;

    while (n -- )
    {
        int x;
        cin >> x;

        int s = 0;
        for (int i = 1; i * i <= x; i ++ )
            if (x % i == 0)
            {
                if (i < x) s += i;
                if (i != x / i && x / i < x) s += x / i;
            }

        if (s == x) printf("%d is perfect\n", x);
        else printf("%d is not perfect\n", x);
    }

    return 0;
}