实验三 循环

#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;
} 

#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;
} 

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

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

		
	} }
	printf("\n");
	printf("101~200之间有%d个素数",x);
	return 0;
	
	
}

#include<stdio.h>
#include<math.h>
int main()
{
	 long int a;
	int b;
    int sum;
	int count;
	int number;
	b=0;
	sum=0;
	count=1;
	number=0;

	printf("Enter a number:");
	scanf("%ld",&a);
	while(a!=0)
	{
	    b=a%10;
		a=a/10;
		
		if(b%2==1){
			sum=sum+b*count;
			
			number++;
			count=pow(10,number);
		}
		
		
	}
	printf("%ld",sum);
	
return 0;
}