实验三

试验任务一

#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;
}

试验任务二

#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;
}

实验任务三

#include <stdio.h>
#include <stdlib.h>
int main() {
    int i, j;
    int n = 0;
    for (i = 100; i <= 200; i++) {
        for (j = 2; j < i; j++) {
            if (i % j == 0)
                break;
        }
        if (j == i)
        {
            printf("%d ", i);
            n++;
        }
    }
    printf("\n101到200之间共有%d个素数\n", n);
    system("pause");
    return 0;
}

试验任务四

#include<stdio.h>
#include<math.h>
int main(void){
    long s;
    printf("Enter a number:");
    while(scanf("%ld",&s)!=EOF){
        int t,i,k,j=0,x=0,y=0;
        t=s;
        for(i=1;t/(10,i)!=0;i++);
        for(k=1;k<=i;k++){
            j=s%10;
            s=s/10;
            if(j%2!=0){
            x=pow(10,y)*j+x;
            y++;
        }
        }
        printf("new number is:%ld\n",x);
        printf("Enter a number:");
    }
        }

试验任务五

#include<stdio.h>
int main(void){
    double s,i,j,k,t;
    int n;
    printf("Enter n(1~10):"); 
    while(scanf("%d",&n)!=EOF){
            s=0,t=-1,k=1;
    for(i=1;i<=n;i++){
        for(j=1;j<=i;j++){
            k=k*j;
        }
        t=t*(-1);
        s=s+t*(1/k);
        k=1;
    }
    printf("n=%d,s=%f\n",n,s);
    printf("Enter n(1~10):");
}
     return 0;
}

试验任务六

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main(){
    int x,n,m=3;
    srand(time(0));
    x=rand()%31+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):");
    while(m--){
       scanf("%d",&n);
       if(n==x){
       printf("恭喜你，猜中了");
       break;
    }
       else if(n<x)
       printf("你猜的日期早了，luck day还没到呢\n");
       else if(n>x)
       printf("你猜的日期晚了，luck day溜到前面啦\n");
       if(m>0)
       printf("再猜(1~31):");
    }
     if(m==-1)
     printf("次数用光啦。偷偷告诉你:12月，你的luck day是%d号",x);
     return 0;
    }