求C语言大佬帮忙 我是入门小白

这个怎么把for文转变为while文 #include #include #define E 0.00001 extern double f(double x); void main() { double a=-3.0,b=3.0,c; for(;;) { if(fabs(b-a) < E) break; c=(a+b)/2.0; if(f(c)==0.0) break; else if(f(a)*f(c) > 0.0) a=c; else b=c; } printf("x=%10.5f\n",c); } double f(double x) { return(x*x*x+3.0*x*x+3.0*x+1.0); }

for(;;)换成whie(true)就可以了。代码如下：

#include <math.h>
#include <stdio.h>
#define E 0.00001 
extern double f(double x); 
void main() 
{ 
	double a=-3.0,b=3.0,c; 
	while(true) //for(;;) 
	{ 
		if(fabs(b-a) < E) 
			break; 
		c=(a+b)/2.0; 
		if(f(c)==0.0) 
			break; 
		else if(f(a)*f(c) > 0.0) 
			a=c; 
		else b=c; 
	} 
	printf("x=%10.5f\n",c); 
} 
double f(double x) 
{ 
	return(x*x*x+3.0*x*x+3.0*x+1.0); 
}

你代码里都是用break退出循环，for就是个无条件死循环，和while(true)是一样的效果，所以直接换成while(true)就满足你需求了

如果希望while有终止条件，那么这么写

#define E 0.00001 
extern double f(double x); 
void main() 
{
	double a = -3.0, b = 3.0, c = (a + b) / 2.0;;
	while ((fabs(b - a) >= E) && f(c) != 0)
	{ 
		if(f(a)*f(c) > 0.0) 
			a=c; 
		else 
			b=c;
		c = (a + b) / 2;
	} 
	printf("x=%10.5f\n",c); 
} 
double f(double x) 
{ 
	return(x*x*x+3.0*x*x+3.0*x+1.0); 
}

while(abs(b-a) < E || f(c)==0.0)

{

c=(a+b)/2.0;

if(f(a)*f(c) > 0.0)

 a=c;

else

 b=c;

}

 #include #include 
 #define E 0.00001  extern double f(double x); 
 void main() { 
    double a=-3.0,b=3.0,c;
    while(abs(b-a) < E || f(c) == 0.0){
        c = (a + b) / 2.0;
        if(f(a) * f(c) > 0.0){
            a = c;
        }else{
            b = c;
        }
        printf("x=%10.5f\n",c); 
    } 
     double f(double x) { 
         return(x*x*x+3.0*x*x+3.0*x+1.0); 
    }

你原代码的include导入库应该有问题，记得回去贴回原来的库