实验三

1.实验任务1

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#include<windows.h>
#define N 80

void print_text(int line, int col, char text[]);
void print_spaces(int n);
void print_blank_lines(int n);

int main()
    {
        int line,col,i;
        char text[N] = "hi, April~";
    
        srand(time(0));

        for(i = 1;i <= 10;++i)
        {
            line = rand() % 25;
            col = rand() % 80;
            print_text(line,col,text);
            Sleep(1000);
        }

    return 0;

    }


void print_spaces(int n)
{
    int i;

    for(i = 1;i<=n; ++i)
        printf(" ");
}


void print_blank_lines(int n)
{
    int i;

    for(i = 1;i <= n;++i)
        printf("\n");
}


void print_text(int line, int col, char text[])
{
    print_blank_lines(line-1);
    print_spaces(col-1);
    printf("%s",text);
}

在屏幕上二维坐标点随机生成“hi,April~”，单个语句长度为8个字符，N为80，总共生成十个语句。

2.实验任务2

task2_1.c

#include<stdio.h>
#include<stdlib.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));

    system("pause");
    return 0;
}


long long fac(int n)
{
    static long long p = 1;

    p = p * n;

    return p;
}

task2_2.c

#include<stdio.h>
#include<stdlib.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);

    system("pause");
    return 0;
}


int func(int a, int b)
{
    static int m = 0,i =2;

    i = i + m + 1;
    m = i + a + b;

    return m;
}

局部static变量的特性：数据存储在静态存储区，函数退出时变量始终存在，再次进入该函数时，将不再重新赋值，直接使用上一次的结果。

3.实验任务3

#include<stdio.h>
#include<stdlib.h>

long long func(int n);

int main()
{
    int n;
    long long f;

    while(scanf("%d",&n)!=EOF)
    {
        f = func(n);
        printf("n = %d,f = %lld\n",n,f);
    }

    system("pause");
    return 0;
}


long long func(int n)
{
    int i=1;
    long long p=1;
    for(;i<=n;i++)
    {
        p = p * 2;

    }
        return p-1;
}

4.实验任务4

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

int main()
{
    int n,m;

    while(scanf("%d%d",&n,&m)!=EOF)
        printf("n = %d,m = %d,ans = %d\n",n,m,func(n,m));

    system("pause");
    return 0;
}

int func(int n,int m)
{    int s;
    if(n==m||n!=0&&m==0)
        return 1;
    if(n<m)
        return 0;
    else
        {s=func(n-1,m)+func(n-1,m-1);
    return s;}
}

5.实验任务5

task5_1.c

#include<stdio.h>
#include<stdlib.h>
double mypow(int x,int y);

int main()
{
    int x,y;
    double ans;

    while(scanf("%d%d",&x,&y)!=EOF)
    {
        ans = mypow(x,y);
        printf("%d的%d次方:%g\n\n",x,y,ans);
    }

    system("pause");
    return 0;
}

double mypow(int x,int y)
{
    double s = 1;
    int i = 1;
    if(y>=0)
        {for(;i<=y;i++)
            {s = s * x;}
        }
    if(y<0)
    {for(;i<=abs(y);i++)
        {s = s / x;}
    }

    return s;
}

task5_2.c

#include<stdio.h>
#include<stdlib.h>
double mypow(int x,int y);

int main()
{
    int x,y;
    double ans;

    while(scanf("%d%d",&x,&y)!=EOF)
    {
        ans = mypow(x,y);
        printf("%d的%d次方:%g\n\n",x,y,ans);
    }

    system("pause");
    return 0;
}

double mypow(int x,int y)
{
    double s=1;
    if(y==0)
        return 1;
    if(y>0)
        {s = x * mypow(x,y-1);
        return s;}
    if(y<0)
        {s = s / mypow(x,-y);
        return s;}
}

6.实验任务6

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
void hanoi(unsigned int n,char from,char temp,char to);
void moveplate(unsigned int n,char from,char to);
int main()
{
    unsigned int n;
    int m;
    while(scanf("%u",&n)!=EOF)

        {
            m = pow(2,n);
            hanoi(n,'A','B','C');
            printf("一共移动了%d次\n\n",m-1);
        }

    system("pause");
    return 0;
}
void hanoi(unsigned int n,char from,char temp,char to)
{
    if(n==1)
        moveplate(n,from,to);
    else
    {
        hanoi(n-1,from,to,temp);
        moveplate(n,from,to);
        hanoi(n-1,temp,from,to);
    }
}
void moveplate(unsigned int n,char from,char to)
{
    printf("%u:%c-->%c\n",n,from,to);
}

7.实验任务7

#include<stdio.h>
#include<stdlib.h>
#include<math.h>
int is_prime(int n);
int main()
{    
    int n,i,p = 1,q,p_flag = 1,q_flag = 1;
    for(n=2;n<=20;n++)
    {    if(n%2 == 1)
            continue;
        if(n>2&&n%2 == 0)
            {    p = 1;
                do
                {    
                    p = p + 1;
                    q = n - p;
                    p_flag = is_prime(p);
                    q_flag = is_prime(q);
                }while(p_flag * q_flag == 0);
                printf("%d = %d + %d\n",n,p,q);
            }        
    }
    system("pause");
    return 0;
}

int is_prime(int n)
{
    int i;
    for(i=2;i<=sqrt(n);++i)
    {
        if(n%i==0)
            break;
    }
    if(n>1&&i>sqrt(n))
        return 1;
    else
        return 0;

}

8.实验任务8

#include<stdio.h>
#include<stdlib.h>
long long func(long s);
int main()
{

    long s,t;

    printf("Enter a numner:");
    while(scanf("%ld",&s)!=EOF)
    {
        t = func(s);
        printf("new number is: %ld\n\n",t);
        printf("Enter a number:");
    }

    system("pause");
    return 0;
}

long long func(long s)
{
    int d;
    long s1 = 1;
    long m = 0;
    while(s>0)
    {
        d = s % 10;
        if(d%2)
        {
            m = s1 * d + m;
            s1 = s1 * 10;
        }
        s = s / 10;
    }
    return m;
}