实验3

ex.1   解一元二次方程

#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;
} 

ex.2　　猜数游戏

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

int main() {
	int guessNumber;
	int ans;
	
	srand((time(0)));
	guessNumber = 1 + rand()%100; 
	
	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");
	 
	return 0;
} 

ex.3     找出最大数和最小数　　

#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;
} 

ex.4    求100到200中的素数　　

#include<stdio.h>
#include<math.h>
int isprime(int n);
int main()
{
	int i;
	for(i=100;i<=200;i++)
	{
		if(isprime(i))
		     printf("%4d",i);
	}
	return 0;
 } 
 int isprime(int n)
 {
 	int k;
 	for(k=2;k<=sqrt(n);k++)
 	     if(n%k==0)
 	         return 0;
 	     return 1;
 }

　　

ex.5   从一个数中找出奇数并组成新的数

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

　　

实验小结：实验中的错误：part2中填空第一个写成n<=5

part3中第二个编程练习个位数若是奇数一开始没有输出