《C++中的常见函数——例题+代码实现 | CSDN创作打卡》

804. n的阶乘

https://www.acwing.com/problem/content/806/

#include 
using namespace std;

int fact(int n)
{
    int a = 1;
    for (int i = 1; i <= n; i ++ ){
        a *= i;
    }
    return a;
}

int main()
{
    int n;
    cin >> n;
    cout << fact(n) << endl;
    
    return 0;
}

 805. x和y的最大值

https://www.acwing.com/problem/content/807/

#include 
using namespace std;

int max(int a,int b)
{
    if(a < b) return b;
    return a;
}

int main()
{
    int a,b;
    cin >> a >> b;
    cout << max(a,b) << endl;
    
    return 0;
}

808. 最大公约数

https://www.acwing.com/activity/content/problem/content/1998/

#include 
#include 
using namespace std;

int gcd(int a,int b)
{
    for (int i = min(a,b); i > 0; i -- ){
        if(a % i == 0 && b % i == 0) return i;
    } 
}

int main()
{
    int a,b;
    cin >> a >> b;
    cout << gcd(a,b) << endl;
    
    return 0;
}

811. 交换数值

https://www.acwing.com/problem/content/813/

#include 
#include 
using namespace std;

void swap(int &a,int &b)
{
    int temp = 0;
    temp = a;
    a = b;
    b = temp;
}

int main()
{
    int a,b;
    cin >> a >> b;
    swap(a,b);
    cout << a << " " << b << endl;
    
    return 0;
}

 812. 打印数字

https://www.acwing.com/problem/content/814/

#include 
#include 
using namespace std;

void printf(int st[],int b)
{
    for (int i = 0; i < b; i ++ )
    cout << st[i] << ' ';
}

int main()
{
    int a,b;
    cin >> a >> b;
    int st[a] = {0};
    for (int i = 0; i < a; i ++ )
    cin >> st[i];
    printf(st,b);
    
    return 0;
}

813. 打印矩阵

https://www.acwing.com/problem/content/815/

#include 
using namespace std;
const int N = 100;
void printf2D(int st[][N], int a, int b)
{
    for (int i = 0; i < a; i ++ ){
        for (int j = 0; j < b; j ++ ){
            cout << st[i][j] << ' ';
        }
        cout << endl;
    }
}

int main()
{
    int a,b;
    cin >> a >> b;
    int st[N][N] = {0};
    for (int i = 0; i < a; i ++ ){
        for (int j = 0; j < b; j ++ ){
            cin >> st[i][j];
        }
    }
    printf2D(st,a,b);
    
    return 0;
}

819. 递归求阶乘

https://www.acwing.com/problem/content/821/

#include 
using namespace std;

int a;
int dfs(int a)
{
    if(a == 1) return 1;
    else return a*dfs(a-1);
}

int main()
{
    cin >> a;
    cout << dfs(a) << endl;
    
    return 0;
}

 820. 递归求斐波那契数列

https://www.acwing.com/problem/content/description/822/

#include 
using namespace std;
int a;
int dfs(int n)
{
    if(n <= 2) return 1;
    else return dfs(n-1) + dfs(n-2);
}

int main()
{
    cin >> a;
    cout << dfs(a) << endl;
    return 0;
}