实验四

#include<stdio.h>
#include<math.h>
void fun(double a,double b,double c) {
    double x1,x2;
    double delta,real,imag;
    if(a==0) printf("not a 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);
        }
    }
    }
    
int main(){
    double a,b,c;
    printf("输入a,b,c:");
    while(scanf("%lf%lf%lf",&a,&b,&c)!=EOF){
        fun(a,b,c);
        printf("输入a,b,c:");
    }
    return 0;
}

 

return 的值有什么约定吗，不知道也没有什么具体的区别；

 

 

task2

#include<stdio.h>
long long fac(int n) { 
    static long long p = 1; 
    p = p*n;
    printf("p = %lld\n", p);
    return p; 
    } 
int main(){
    int i,n;
    printf("输入n:");
    scanf("%d",&n);
    for(i=1;i<=n;++i){
        printf("%d!=%lld\n",i,fac(i));
    }
    return 0;
}

局部变量会在每一次执行时改变自己的值

 

task2-2

#include<stdio.h>
int func(int, int);
int main() {
    int k=4,m=1,p1,p2;
    
    p1 = func(k,m) ; 
    p2 = func(k,m) ;
    printf("%d,%d\n",p1,p2) ;
    
    return 0;    
}

int func(int a,int b) {   
    static int m=0,i=2;
    
    i += m+1;
    m = i+a+b;  
    
    return (m);
}

 

 task3

#include<stdio.h>
#define N 1000
int fun(int n,int m,int bb[N]){
    int i,j,k=0,flag;
    
    for(j=n;j<=m;j++){
        flag=1;
        for(i=2;i<j;i++)
            if(j%i==0){
                flag=0;
                break;
            }
        if(flag)
            bb[k++]=j;    
    }
    return k;
}

int main(){
    int n=0,m=0,i,k,bb[N];
    scanf("%d",&n);
    scanf("%d",&m);
    
    for(i=0;i<m-n;i++)
        bb[i]=0;
    k=fun(n,m,bb);
    for(i=0;i<k;i++)
        printf("%4d",bb[i]);
    
    return 0;        
}

 

 task4

#include<stdio.h>
long long fun(int n);

int main(){
    int n;
    long long f;
    
    while(scanf("%d",&n)!=EOF){
        f=fun(n);
        printf("n=%d,f=%lld\n",n,f);
    }
    return 0;
}
long long fun(int n){
    int i;
    long long f=1;
    for(i=1;i<=n;i++)
        f=2*f;
    
    return f-1;
}

 

 

task5

#include<stdio.h>
void draw(int n,char symbol){
    int i,m,k;
    for(i=1;i<=n;i++){
        for(m=1;m<=n-i;m++)
            printf(" ");
        for(k=1;k<=2*i-1;k++)
            printf("%c",symbol);
    printf("\n");
    }
}

int main(){
    int n;
    char symbol;
    
    while(scanf("%d %c",&n,&symbol)!=EOF){
        draw(n,symbol);
        printf("\n");
    }
    return 0;
}