实验四
#include <stdio.h> #include <math.h> void solve(double a,double b,double c); int main(){ double a,b,c; printf("Enter a b c:"); while(scanf("%lf%lf%lf",&a,&b,&c)!=EOF){ solve(a,b,c); printf("Enter a b c:"); } return 0; } void solve(double a,double b,double c){ double x1,x2; double delta,real,imag; if(a==0) printf("not quadratic equation.\n"); else{ delta=b*b-4*a*c; if(delta>=0){ x1=(-b+sqrt(delta))/(2*a); x1=(-b-sqrt(delta))/(2*a); printf("x1=%f,x2=%f\n",real,imag); } else{ real=-b/(2*a); imag=sqrt(-delta)/(2*a); printf("x1=%f+%fi,x2=%f-%fi\n",real,imag,real,imag); } } }
返回值只能有一个,不能多个返回,一元二次方程可能会返回两个值
//利用局部static变量计算阶乘 #include <stdio.h> long long fac(int n); int main(){ int i,n; printf("Enter n:"); scanf("%d",&n); for(i=1;i<=n;i++) printf("%d!=%11d\n",i,fac(i)); return 0; } long long fac(int n){ static long long p=1; printf("p=%11d\n",p); p=p*n; return p; }
//利用局部static变量计算阶乘 #include <stdio.h> long long fac(int n); int main(){ int i,n; printf("Enter n:"); scanf("%d",&n); for(i=1;i<=n;i++) printf("%d!=%11d\n",i,fac(i)); return 0; } long long fac(int n){ static long long p=1; p=p*n; return p; }
#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); }
首先a=k=4,b=m(主函数)=1,那么i=2+1+0=3,m=3+4+1=8;p2:a=k=4,b=m(主函数)=1, static m为静态变量,m=8,i=3+8+1=12,所以m=12+4+1=17
在修饰变量的时候,static 修饰的静态局部变量只执行初始化一次
//寻找两个整数之间的所有素数(包括这两个整数),把结果保存在数组bb中,函数返回素数的个数。 // 例如,输入6和21,则输出为:7 11 13 17 19。 #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==1) 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; }
#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){ long long int f; if(n==1) f=1; else f=2*fun(n-1)+1; return f;
#include <stdio.h> void draw(int n,char symbol); #include <stdio.h> int main(){ int n,symbol; while(scanf("%d %c",&n,&symbol)!=EOF){ draw(n,symbol); printf("\n"); } return 0; } void draw(int n,char symbol){ int i,k; for(k=1;k<=n;k++){ for(i=1;i<=n-k;i++){ printf(" "); } for(i=1;i<=2*k-1;i++){ printf("%c",symbol); } printf("\n"); } }