实验三

#include <math.h>
#include <stdio.h>
#include <stdlib.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)) {
        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 = %f, x2 = %f\n", x1, x2);
            }
            else {
                real = -b/(2*a);
                imag = sqrt(-delta) / (2*a);
                printf("x1 = %f + %fi, x2 = %f - %fi\n", real, imag, real, imag);
            }
        }
        
        printf("Enter a, b, c:\n");
    }
    system("pause");
    return 0;
} 

2

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

int main() {
    int guessNumber; // 存放程序运行时生成的1~100之间的随机整数 
    int ans;     // 存放用户猜的数字 
    
    srand((time(0)));  // 以时间函数作为随机种子 
    guessNumber = 1 + rand()%100;  // 生成1~100之间的随机数 
    
    do {
        printf("your guess number is(1~100): ");
        scanf("%d", &ans);
        if(ans < guessNumber)
            printf("%d is lower than the number.\n", ans);
        else if(ans > guessNumber) 
            printf("%d higher then the number.\n", ans); 
    }while(ans != guessNumber);
    
    printf("Congratulations. you hit it~\n");    
    
    system("pause"); // 在devc中运行时，这一行可以去掉
     
    return 0;
} 

3

#include <stdio.h>
#include <stdlib.h>
int main() {
    int number, max, min, n;
    
    n=1;
    printf("输入第%d个数: ", n);
    scanf("%d", &number);
    max = number;
    min = number;
    
    while(n<5) {
        n++;
        printf("输入第%d个数: ", n);
        scanf("%d", &number);    

        if(max<number)
            max = number;
        else if(min>number)
            min = number;
    }
    
    printf("最大数为: %d\n", max);
    printf("最小数为: %d\n", min);
    
    system("pause");
    
    return 0;
} 

4

#include<stdio.h>
#include<math.h>
#include<stdlib.h>
int isprime(int n);
int main(){
    int i,x;
    x=0;
    for(i=101;i<=200;i++){
        if(isprime(i)){
            printf("%4d",i);
            x++; 
        }
    }
    printf("共有%ld个素数",x);
    return 0;    
} 
int isprime(int n){
    int k;
    for(k=2;k<=sqrt(n);k++){
        if(n%k==0)
            return 0;
    }
    return 1;
}

5

#include <stdio.h>
#include <math.h>
int main(){
    long int s;
    int n,i=1;
    scanf("%ld",&s);
    if(s<10){
        s%2==1;
        printf("%ld",s);
    }
    else{
        do{
            do{
                i=i*10;
                n=s/i;
            }
        while(n>=10);
            if(n%2==1)
                printf("%d",n);
                s=s-n*i;
                i=1;
       }
    while(s>=10);
        if(s%2==1)
            printf("%ld",s);
    }
    return 0;
}

来源：https://www.cnblogs.com/wangshuodi1447216674/p/11886809.html