实验3

#include <math.h>
#include <stdio.h>
int main(){
    float a, b, c, x1, x2;
    float delta, real, imag;
    printf("Enter a,b,c:   ");
    while (scanf("%f%f%f", &a, &b, &c) != EOF) {
        if (a == 0)
            printf("not quadratic equation.\n\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\n", x1, x2);
            }
            else {
                real = -b / (2 * a);
                imag = sqrt(-delta) / (2 * a);
                printf("x1=%.2f+&.2fi,x2=%.2f-%.2fi\n\n", real, imag, real, imag);
            }
        }
        printf("Enter a,b,c");
    }
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 5

int main(){
    int x, n;
    
    srand(time(0));
    n = 0;
    do {
        n++;
        x = rand()%10;
        printf("%3d",x);
    }while(n<N);
     
     printf("\n");
     
     return 0;
}

#include <stdio.h>
int main(){
    int m, n;
    int count = 0;
    
    for (m=101;m<=200;m++){
        for(n=2;n<m;n++){
            if(m%n==0)
            break;
        }
        if(n>=m){
            count++;
            printf("%d",m);
            if(count % 5 == 0)
            printf("\n");
        }
    }
    return 0;
} 

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

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

int main(){
    double i, sum=0, p, q=1, x=-1;
    int n;
    printf("Enter n(1~10);");
    scanf("%d",&n);
    if(n<1&&n>10)
{
    printf("输入数据错误!\n");
    }
    for(i=1;i<=n;i++)
{   p=1/i;
    q=p*q;
    sum=sum+pow(x,(i-1))*q;
    }
    printf("n = %d s = %lf\n",n,sum);
    return 0;
} 

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main(){
    int n, x, i=1;
    printf("猜猜2020年12月哪一天会是你的luck day\n");
    printf("开始喽，你有三次机会，猜吧(1~31):");
    srand(time(0));
    x= rand()%32;
    scanf("&d",&n);
    while(i<3){
        if(n == x){
            printf("猜中啦！你的luck day是%d号",x);
            break;
        }
        else if(n<x){
            printf("你猜的日期早了，luck day还在后面呢\n");
            i++; 
        }
        else if(n>x){
            printf("你猜的日期晚了，luck day悄悄溜到前面啦\n");
            i++;
        }
        printf("再猜（1~31）；");
        scanf("%d",&n); 
    }
    if(i=3){
        printf("次数用完啦，偷偷告诉你，12月，你的luck day是%d号\n",x);
    } 
    return 0;
}