二分法求根，出现什么问题啦

[zzcwyu]

#include <iostream>
#include <cmath>
using namespace std;
double f(double a){
double y=exp(a)+10*a-2;
return y;
}
int main(){
int n,i=0;
double a,b,e1,e2,x;
cout<<"please input a,b,e1,e2,n;"<<endl;
cin>>a>>b>>e1>>e2>>n;
double y1=f(a);
double y2=f(b);

if(y1*y2>0) cout<<"fail to get the answer:"<<endl;
else{
do{
x=(a+b)/2;
if(f(x)<e1)
{
cout<<i+1<<" "<<x<<" "<<f(x)<<endl;
break;
}
else{
if(y1*f(x)<0) {
b=x;
y2=f(x);
i++;
}
else {
a=x;
y1=f(x);
i++;
}
}
cout<<i<<" "<<x<<" "<<f(x)<<endl;
}while(abs(b-a)>e2);
}return 0;
}



如题

[zzcwyu]

我也查不出问题，但结果就是不对，n是题目要求

[langhua0001]

输入
0.0
1.0
0.001
0.0001
9

你要是再说不对，那我就无语了

DEV-C++ C++BUILDER 都可以正常输出

[langhua0001]

[Quote=引用楼主 zzcwyu 的帖子:]


#include <iostream>
#include <cmath>
using namespace std;
double f(double a){
double y=exp(a)+10*a-2;
return y;
}
int main(){
int n,i=0;
double a,b,e1,e2,x;
cout < <"please input a,b,e1,e2,n;" < <endl;
cin>>a>>b>>e1>>e2>>n;
double y1=f(a);
double y2=f(b);

if(y1*y2>0) cout < <"fail to get the answer:" < <endl;
else{
do{
x=(a+b)/2;
if(f(x) <e1) 改为 :if(fabs(f(x))<e1) 要取绝对值
{
cout …
[/Quote]

[zzcwyu]

还是不行，执行结果还是
输入：0.0 1.0 0001 0.0001 9
输出只有：1 0.5 4.64872：

[zzzlll1983]

??

[langhua0001]

#include <cstdlib>
#include <iostream> 
#include <cmath> 
using namespace std; 
double f(double a)
{ 
  double y = exp(a)+10*a-2; 
  return y; 
} 
int main()
{ 
  int n,i=0; 
  double a,b,e1,e2,x; 
  cout <<"please input a,b,e1,e2,n;" <<endl; 
  cin>>a>>b>>e1>>e2>>n; 
  double y1=f(a); 
  double y2=f(b); 

  if(y1*y2>0) 
              cout <<"fail to get the answer:" <<endl; 
  else
  { 
    do
    { 
      x=(a+b)/2; 
      if(fabs(f(x)) <e1 ) 
      { 
        cout <<i+1 <<" " <<x <<" " <<f(x) <<endl; 
        break; 
        } 
    else
    { 
      if(y1*f(x) <0) 
      { 
        b=x; 
        y2=f(x); 
        i++; 
      } 
      else 
      { 
        a=x; 
        y1=f(x); 
        i++; 
      } 
    } 
    cout <<i <<" " <<x <<" " <<f(x) <<endl; 
    }while(abs(b-a)>e2); 
  }
  system("pause");
  return 0; 
} 

没问题的 

另外想问楼主一下n起什么作用了...

[zzcwyu]

汗，难道这样说是编译器的问题

[zzcwyu]

abs与fabs的不同啊