初识3

#include<stdio.h>
#include<math.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 quardratic 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 n,m,num,N;
	N=0;
	for( n=101;n<200;n++){
	    
	    num=0;
	    for( m=1;m*m<=n;m++){
	
	        if(n%m==0){
	
		    num++;
            }
        }
        
        if(num<=1){
        	printf("%d\t",n);
        	N++;
		}

    }
	printf("素数的个数是%d",N);
	
}

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

#include<stdio.h>
#include<math.h>
int main(){
	int x,m,i;
	i=1;
	m=1;
	float s=0;
	printf("请输入1~10之间的整数:"); 
	while(scanf("%d",&x)!=EOF){
	
	if(x>=1||x<=10){
		do{
			m=m*i;
			i++;
			s=s+pow((-1),i)/m;
		}while(i<=x);
	}
	else{
		printf("请注意审题");
	}
	printf("s=%f\n",s);
	printf("请输入1~10之间的整数:");
}
}

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int main(){
    int x,n,i;
    srand(time(0));
    n=0;
    x=rand()%31;
        printf("猜猜看2020年12月哪天会是你的luck day\n\n");
        printf("开始喽，你有三次机会，猜猜看吧(1~31): ");
    for(i=1;i<=3;++i){
    if(i>=2){
        printf("再猜:"); 
    }
    scanf("%d",&n);
    printf("\n");
     if(n<x){
            printf("你猜的日期早啦,luck day还没有来到呢\n\n");
        }
         if(n==x){
            printf("你猜对了");
            break;
        }
         if(n>x){
            printf("你猜的日期晚啦,luck day悄悄溜到前面拉\n\n");
        }
    if(i==3){
            printf("次数用完啦,悄悄告诉你,12月,luck day是%d号",x);
        }
        }
    printf("\n\n");
    return 0;
}