Re: [問題] 小新手程式寫不出來，麻煩高手幫忙。

看板Programming作者cxzdsa5566 (cxzdsa5566)時間13年前 (2010/10/06 23:05)推噓-1(1推 2噓 5→)

留言8則, 6人參與討論串3/4 (看更多)

#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

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ericinttu

10/06 23:21, , 1^F

10/06 23:21, 1^F

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ericinttu

10/06 23:21, , 2^F

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james732

10/06 23:42, , 3^F

10/06 23:42, 3^F