实验3

任务一

#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;
 }

 

#include<stdio.h>
int func(int, int);

int main()
{
    int k = 4, m = 1, p1, p2;
    
    p1 = func(k, m);
    p2 = func(k, m);
    printf("%d,%d\n", p1, p2);
    
    return 0;
}

int func(int a, int b)
{
    static int m = 0, i = 2;
    
    i += m + 1;
    m = i + a + b;
    
    return (m); 
} 

 static：一次函数调用结束时，该数据不会消失，而是继续被调用，直到程序运行结束。

任务二

迭代

#include<stdio.h>
void printSymbol(int n, char symbol);

int main()
{
    int n;
    char symbol;
    
    while( scanf("%d %c", &n, &symbol) != EOF )
    {
        printSymbol(n, symbol);
        printf("\n"); 
    }
    
    return 0;
}

void printSymbol(int n, char symbol)
{
    int i;
    for(i=1;i<=n;i++)
    {
        printf("%c",symbol);
    }
}

 递归

#include<stdio.h>
void printSymbol(int n, char symbol);

int main()
{
    int n;
    char symbol;
    
    while( scanf("%d %c", &n, &symbol) != EOF )
    {
        printSymbol(n, symbol);
        printf("\n"); 
    }
    
    return 0;
}

void printSymbol(int n, char symbol)
{
    if(n==1)
        printf("%c",symbol);
    else
    {
        printSymbol(n-1,symbol);
        printf("%c",symbol);
     } 
}

 

任务三

#include<stdio.h>
long long fun(int n);

int main()
{
    int n;
    long long f;
    
    while (scanf("%d", &n) != EOF)
    {
        f = fun(n);
        printf("n = %d, f = %lld\n", n, f);
    }
    
    return 0;
}

long long fun(int n)
{
    long long m;
    
    if(n==1)
        m = 1;
    else
        m = fun(n-1)*2+1;
        
    return m;
}

 

任务四

#include<stdio.h>
#include<math.h>
int isPrime(int n);

int main()
{
    int n,j,count=0;
    for(n=101;n<=200;n++)
    {
        j = isPrime(n);
        if(j==0)
        {
            printf("%5d",n);
            count++;
        }
    }
    
    printf("\n101~200之间一共有%d个非素数",count);
    
    return 0;
}

int isPrime(int n)
{
    int k;
    for(k=2;k<=sqrt(n);k++)
    {
        if(n%k==0)
        return 0;
     } 
     return 1;
}

 

任务五

#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)
{
    long x=0,i;
    int t;
    i=1;
    while(s)
    {
        t=s%10;
        if(t%2!=0)
        {
            x=x+t*i;
            i=i*10;
        }
        s=s/10;
    }
    s=x;
}

 

任务六

#include<stdio.h>
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;
}

double fun(int n)
{
    int i;
    double x=-1,y=0;
    for(i=1;i<=n;i++)
    {
        x=-x*i;
        y=y+1/x;
    }
    return y;
}

 

总结：递归是重复调用函数自身实现循环。迭代是函数内某段代码实现循环；迭代时，会当前保存的结果作为下一次循环计算的初始值。