Re: [問題] 小新手程式寫不出來，麻煩高手幫忙。

[cxzdsa5566 (cxzdsa5566)]

#include <iostream>
#include <math.h>
using namespace std;
int main()
{
double a,b,c,z1,z2,z3,z2i,z3i,sita;
cout<<" This program finds the roots of x^3 +a x^2 + b x + c =0 "<<endl;
cout<<" Enter the coefficient a: "; cin>>a;
cout<<" Enter the coefficient b: "; cin>>b;
cout<<" Enter the   constant  c: "; cin>>c;
double Q=(3*b*b-a*a)/9;
double R=(9*a*b-27*c-2*a*a*a)/54;
double D=(Q*Q*Q+R*R*R)/3;

if(D==0) {
z1 = -a/3+2*pow(R,1.0/3.0);
z2 = z3=-a/3+2*sqrt(-Q);
z2i=z3i=0;
}
if (D>0) {
z1 = -a/3+pow((R+sqrt(D)),1.0/3.0)+pow((R-sqrt(D)),1.0/3.0);
z2 = -a/3-(pow(R+sqrt(D),1.0/3.0)+pow(R-sqrt(D),1.0/3.0))/2;
z2i =(pow(R+sqrt(D),1.0/3)-pow(R-sqrt(D),1.0/3.0))*(sqrt(3)*0.5);
z3 = -a/3-(pow(R+sqrt(D),1.0/3.0)+pow(R-sqrt(D),1.0/3.0))/2;
z3i = -(pow(R+sqrt(D),1.0/3.0)-pow(R-sqrt(D),1.0/3.0))*(sqrt(3)*0.5);
}
if (D<0) {
double sita=acos(R/sqrt(-Q*Q*Q));
z1=-a/3+2*sqrt(-Q)*cos(sita/3);
z2=-a/3+2*sqrt(-Q)*cos(sita/3+2*M_PI/3);
z3=-a/3+2*sqrt(-Q)*cos(sita/3+4*M_PI/3);
z2i=z3i=0;
}

cout<<endl;
cout<<" "<<"x^3+"<<a<<" x^2+ "<<b<<" x+ "<<c<<" = 0"<<endl;
cout<<" Root 1: "<<z1<<endl;
cout<<" Root 2: "<<z2<<" + "<<z2i<<"i"<<endl;
cout<<" Root 3: "<<z3<<" + "<<z3i<<"i"<<endl;
system("pause");
return 0;
}


這是最新改好的，

跑出來還是不對，

結果都會寫啥#IND的，

都不是答案，

不過如果a=b=c=0

會算隊就是@@

可以再幫幫忙嗎?

--
※ 發信站: 批踢踢實業坊(ptt.cc) 
◆ From: 140.112.218.123
噓 ericinttu:小改版就要麻煩人debug,有沒有這麼好的
→ ericinttu:事?
→ james732:請學一下debugger: http://ppt.cc/thpN
噓 cooper6334:你應該去C++版，那邊好人比較多
→ cooper6334:pow(負數,小數次方)是算不出來的
推 RedHouse:義大利麵條不好吃
→ horngsh:只愛寫程式,不愛DEBUG的人撐不久
→ LPH66:那邊好人其實是近一陣子比較多 XD