task1

(1)

#include <stdio.h>
long long fac(int n); 
int main()
{
    int i, n;
    printf("Enter n: ");
    scanf("%d", &n);
    for (i = 1; i <= n; ++i)
        printf("%d! = %lld\n", i, fac(i));
    return 0;
}
long long fac(int n)
{
    static long long p = 1;
    p = p * n;
    return p;
}

 (2)

#include <stdio.h>
long long fac(int n); 
int main()
{
    int i, n;
    printf("Enter n: ");
    scanf("%d", &n);
    for (i = 1; i <= n; ++i)
        printf("%d! = %lld\n", i, fac(i));
    return 0;
}
long long fac(int n)
{
    static long long p = 1;
    printf("%lld\n", p);
    p = p * n;
    return p;
}

 (3)

static变量只赋初值一次，在程序运行时它已经具有值，以后每次调用函数时不再赋初值而保留上次函数调用结束后的值

 

 

 

 

task2

（1）递归

#include <stdio.h>
void printSymbol(int n, char symbol); // 函数声明
int main()
{
    int n;
    char symbol;
    while (scanf("%d %c", &n, &symbol) != EOF)
    {
        printSymbol(n, symbol); // 函数调用
        printf("\n");
    }
    return 0;
}
void printSymbol(int n, char symbol)
{
    if (n == 1)
        printf("%c", symbol);
    else
    {
        printSymbol(n - 1, symbol);
        printf("%c", symbol);
    }
}

 （2）迭代

#include <stdio.h>
void printSymbol(int n, char symbol); // 函数声明
int main()
{
    int n;
    char symbol;
    while (scanf("%d %c", &n, &symbol) != EOF)
    {
        printSymbol(n, symbol); // 函数调用
        printf("\n");
    }
    return 0;
}
void printSymbol(int n, char symbol)
{
    int i;
    for (i = 1; i <= n; i++)
    {
        printf("%c", symbol);
    }
}

 

 

 

 

 

 task3

#include <stdio.h>
long long fun(int n);
int main()
{
    int n;
    long long f;
    while (scanf("%d", &n) != EOF)
    {
        f = fun(n)-1; 
        printf("n = %d, f = %lld\n", n, f);
    }
    return 0;
}
long long fun(int n)
{
    long long t;
    if (n == 1)
    {
        t = 2;
    }
    else
    {
        t = 2 * fun(n - 1);
    }
    return t;
}

 

 

 

 

 

 task4

#include<stdio.h>
#include<math.h>
int isprime(unsigned int x);
int main()
{
    unsigned int y;
    int k = 0;
    for (y = 101; y <= 200; y++)
    {
        if (isprime(y) == 0)
        {
            printf("%u  ", y);
            k++;
        }
    }
    printf("\n");
    printf("101~200之间共有%d个非素数",k);
}
int isprime(unsigned int x)
{
    int i, k;
    k = sqrt(x);
    for (i = 2; i <= k; i++)
    {
        if (x % i == 0)
            return 0;
        else if (i > k)
            return 1;
    }
}

 

 

 

 

task5

#include <stdio.h>
long fun(long s);
int main()
{
    long s, t;
    printf("Enter a number: ");
    while (scanf("%ld", &s) != EOF)
    {
        t = fun(s);
        printf("new number is: %ld\n\n", t);
        printf("Enter a number: ");
    }
    return 0;
}
long fun(long s)
{
    unsigned long n = 0, i, k;
    int t;
    i = s;
    k = 1;
    while (i != 0)
    {
        t = i % 10;
        if (t % 2!=0)
        {
            n = n + t * k;
            k = 10 * k;
        }
        i = i / 10;
    }
    return n;
} 

 

 

 

 

 

task6

#include <stdio.h>
unsigned int jc(unsigned int x);
double fun(int n);
int main()
{
    int n;
    double s;
    printf("Enter n(1~10): ");
    while (scanf("%d", &n) != EOF)
    {
        s = fun(n); 
        printf("n = %d, s= %f\n\n", n, s);
        printf("Enter n(1~10): ");
    }
    return 0;
}
unsigned int jc(unsigned int x)
{
    unsigned int result;
    if (x == 0)
    {
        result = 1;
    }
    else
    {
        result = x * jc(x - 1);
    }
    return result;
}
double fun(int n)
{
    int top = 1, botton, m = 1;
    unsigned int i;
    double s,sum=0;
    for (i = 1; i <= n; i++)
    {
        botton = jc(i);
        s = top*1.0 / botton;
        sum = sum + s*m;
        m = -m;
    }
    return sum;
}