实验三

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 5
int main() {
     int x, n;
     srand(time(0));
     for(n=1; n<=N; n++) {
         x = rand() % 100;
         printf("%3d", x); 
    }
    printf("\n");
    return 0;
}

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

int main(){
    int x, n, a;
    srand(time(0));
    x = rand() % 31 + 1;
    n = 0;
    printf("猜猜2021年5月哪一天是你的幸运日？\n开始喽，你有三次机会，猜吧（1~31）：");
    while(n<3){
        scanf("%d", &a);
        
        if (a==x)
        {
        printf("猜对了！");
        break;
        }
        else if (a<x)
         {
             if (n<3)
                printf("早了，好日子在后头。\n再猜:");
             else
                 printf("早了，好日子在后头。");
         }
        else
         {
             if (n<3)
                printf("晚了，好日子在前头。\n再猜:");
            else
                printf("早了，好日子在前头。");
         }
        n++ ; 
            } 
        if (n<3)
        printf("\n");
        else
        printf("次数用完咯，偷偷告诉你：五月，你的幸运日是%d号", x);    

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 5
int main() {
     int x, n;
     srand(time(0));
     for(n=1; n<=N; n++) {
         x = rand() % 100;
         printf("%3d", x); 
    }
    printf("\n");
    return 0;
}

#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) {
    double s=1,a=1;
    int i;
        if (n == 1)
            return 1;
        else{
            for ( i = 2; i <= n; i++){
                a = -a * 1 / i;
                s = s + a;
            }
            return s;
        }
}

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

#include <math.h>
#include <stdio.h>

void solve(double a, double b, double c);
int main() {
    double a, b, c;
    
    printf("Enter a, b, c: ");
    while(scanf("%lf%lf%lf", &a, &b, &c) != EOF) 
    {
        solve(a, b, c);
        printf("Enter a, b, c: ");
    }
    
    return 0;
}
//函数定义
//功能：求解一元二次方程，打印输出结果
//形式参数：a,b,c为一元二次方程系数


void solve(double a, double b, double c) 
{
    double x1, x2;
    double delta, real, imag;
    
    if(a == 0) 
        printf("not quadratic equation.\n");
    else 
    {
        delta = b*b - 4*a*c;
        
        if(delta >= 0) 
        {
            x1 = (-b + sqrt(delta)) / (2*a);
            x2 = (-b - sqrt(delta)) / (2*a);
            printf("x1 = %.2f, x2 = %.2f\n", x1, x2);
        }
        else 
        {
            real = -b/(2*a);
            imag = sqrt(-delta) / (2*a);
            printf("x1 = %.2f + %.2fi, x2 = %.2f - %.2fi\n", real, imag, real, imag);
        }
    }    
}