实验3

task1

#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);
 }

功能：每隔1000ms将指定字符串随机打在屏幕上

task 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;
    
    p = p * n;
    printf("p = %llf\n", p);
    
    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;
}

实验运行结果与理论分析一致。

static变量特性：每次运算后，会保留变量运算后的变量的值，并以此作为下一次函数调用的变量初始值。

task3

#include <stdio.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);
    }
    
    return 0;
}

long long func(int n){
    if(n == 1)
        return 1;

    else
        return func(n - 1) * 2 + 1;
    

}

task4

#include <stdio.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));
    
    
    return 0;
}

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

task5_1

#include <stdio.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);
}
    return 0;
 } 
 
 double mypow(int x, int y){
     int i;
     double ans = 1;
     
     if(y >= 0){
         for(i = 0; i <= y-1; i++)
             ans = ans * x;
         return ans;}
    else
         for(i = 1;i <= -y; i++)
             ans = ans / x;
        return ans; 
 }

task5_2

#include <stdio.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);
}
    return 0;
 } 
 
 double mypow(int x, int y){
     double ans;
     
     if(y == 0)
         return 1;
     
     if(y >= 0){
         ans = mypow(x, y-1) * x;
         return ans;
}
    else
        ans = mypow(x, y+1) / x;
        return ans;

}

task6

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

void hanoi(unsigned int n,char from,char temp,char to);
void moveplate(unsigned int n,char from,char to);
int sum = 0;
int main()
{
    unsigned int n;

    while(scanf("%u", &n) != EOF){
        hanoi(n, 'A', 'B', 'C');
        printf("\n一共移动了%d次。\n", sum);
        sum = 0;
}
    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);
    sum += 1;
    
}

task7

#include <stdio.h>
#include <math.h>
#include <windows.h>
int is_prime(int n);
int main()
{
    int i, a, j, k;
    for(a = 1;a <= 20; a++){
        if((a % 2 == 0)&& (a >= 4)){
            for(i = 1;i < a; i++){
                if(is_prime(i))
                    if(is_prime(a - i)){
                        j = i;
                        k = a - i;}    
            }printf("%d = %d + %d\n", a, j, k);
    }        
}
    return 0;  
}


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

}

task8

#include <stdio.h>
#include <math.h>
long func(long s);

int main()
{
    long s, t;
    
    printf("Enter a number: ");
    while(scanf("%ld", &s) != EOF){
        t = func(s);
        printf("new number is: %ld\n\n", t);
        printf("Enter a number: ");
    }
    
    
    return 0;
 } 
 
 long func(long s){
     int y, a, i = 1;
     while(s != 0){
         y = s % 10;
         if(y != 0 && y % 2 != 0){
            a += y * pow(10, i-1);
            i++;}
        s = s / 10;
        
     }
     return a;
 }