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  1. //Котельникова Любовь, 113 группа, курсовая работа
  2. #include <iostream>
  3. #include <stdlib.h>
  4. #include <stdio.h>
  5. #include <fstream>
  6. #include <cfloat>
  7. #include <clocale>
  8. #include <float.h>
  9. using namespace std;
  10. typedef double (*Func)(double*);
  11. class RungeKut
  12. {
  13.     private:
  14.     int N;
  15. 	Func* FuncArray;
  16.     double *x0;
  17.     double *yR;       //текущий столбец значений-решений
  18.     double t;           //независимая переменная, изменяющаяся от а до b
  19.     const char* stroka;
  20.     public:
  21.     RungeKut(int n);
  22.     void Init(double *X0, Func* Funcarray, const char* a);
  23.     void Start(double T_0, double T_end, double Step);
  24.     ~RungeKut();
  25. };
  26. RungeKut::RungeKut(int n)
  27. {
  28.     N=n; 
  29. 	x0=new double[N];
  30. 	yR=new double[N];
  31. }
  32. void RungeKut::Init(double *X0, Func* Funcarray, const char* a)   
  33. {
  34.     FuncArray=new Func[N];
  35. 	for(int i=0;i<N;i++) {
  36. 		FuncArray[i]=Funcarray[i];
  37. 		x0[i]=X0[i];
  38. 	}
  39.     int len=strlen(a);
  40. 	stroka=new char[len+1];
  41. 	stroka=a;
  42. }
  43. void RungeKut::Start(double T_0, double T_end, double Step)
  44. {
  45. 	ofstream fout(stroka);
  46.     t=T_0;
  47.     int ii=(int)((T_end-T_0)/Step);
  48.     fout<<t;
  49.     for (int j=0;j<N;j++) {
  50. 		fout<<" "<<x0[j];
  51. 		yR[j]=x0[j];
  52. 	}
  53. 	fout<<endl;
  54. 	for(int k=0;k<ii;k++)
  55. 	{
  56. 	   double *K0=new double[N];
  57. 	   double *K1=new double[N];
  58.        double *K2=new double[N];
  59. 	   double *K3=new double[N];
  60. 	   double *Khelp=new double[N];
  61. 	   for(int i=0; i<N;i++){
  62. 		   K0[i]=Step*FuncArray[i](yR);
  63.            Khelp[i]=yR[i]+K0[i]/2;
  64. 	   }
  65. 	   for(int i=0;i<N;i++){
  66. 		   K1[i]=Step*FuncArray[i](Khelp);
  67. 	   }
  68. 	   for(int i=0;i<N;i++){
  69.            Khelp[i]=yR[i]+K1[i]/2;
  70. 	   }
  71. 	   for(int i=0;i<N;i++){
  72. 		   K2[i]=Step*FuncArray[i](Khelp);
  73. 	   }
  74. 	   for(int i=0;i<N;i++){
  75.            Khelp[i]=yR[i]+K2[i];
  76. 	   }
  77. 	   for(int i=0;i<N;i++){
  78. 		   K3[i]=Step*FuncArray[i](Khelp);
  79. 	   }
  80. 	   for(int i=0;i<N;i++){
  81.            yR[i]=yR[i]+(K0[i]+2*K1[i]+2*K2[i]+K3[i])/6;
  82. 	   }
  83. 	   t=t+Step;
  84.        fout<<t;
  85.        for (int j=0;j<N;j++) {
  86. 	   	    fout<<" "<<yR[j];                       // В файле столбики: t,yR[1],yR[2],...,yR[N]
  87. 	        }
  88. 	   fout<<endl;
  89. 	   delete [] K0;
  90.        delete [] K1;
  91. 	   delete [] K2;
  92. 	   delete [] K3;
  93. 	   delete [] Khelp;
  94. 	}
  95. 	fout.close();
  96. }
  97. RungeKut::~RungeKut()
  98. {
  99. 	delete [] x0;
  100. 	delete [] yR;
  101. 	delete [] stroka;
  102. 	delete [] FuncArray;
  103. }
  104. double xxx(double *y)
  105. {
  106. 	//return 5.*(y[1]-y[0]);
  107. 	return y[0];
  108. }
  109. double yyy(double *y)
  110. {
  111. 	//return y[0]*(4.-y[2])-y[1];
  112. 	return y[1];
  113. }
  114. double zzz(double *y)
  115. {
  116. 	//return y[0]*y[1]-y[2];
  117. 	return y[2];
  118. }
  119. int main()
  120. {
  121.     int n=3;
  122.     double a,b,h;
  123. 	a=0;
  124. 	b=100;
  125. 	h=0.01;
  126. 	double *X0=new double[n];
  127. 	/*cout<<"Vvedite stolbets X0 ";
  128. 	for (int i=0;i<n;i++) {
  129. 		cin>>X0[i];
  130. 	}*/
  131. 	X0[0]=0.1;
  132. 	X0[1]=0.1;
  133. 	X0[2]=0.1;
  134.     if ((X0[0]==0)&&(X0[1]==0)&&(X0[2]==0)) {
  135.         double a=DBL_EPSILON;
  136.         X0[0]=X0[1]=X0[2]=a;
  137.     }
  138. 	Func* Funcarray=new Func[n];
  139. 	Funcarray[0]=xxx;
  140. 	Funcarray[1]=yyy;
  141.     Funcarray[2]=zzz;
  142.     RungeKut rk=RungeKut(n);
  143.     rk.Init(X0,Funcarray, "ab.txt");
  144.     rk.Start(a,b,h);
  145.     return 0;
  146. }
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin
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Standard input is empty
compilation info 
prog.cpp: In member function ‘void RungeKut::Init(double*, double (**)(double*), const char*)’:
prog.cpp:39:21: error: ‘strlen’ was not declared in this scope
     int len=strlen(a);
                     ^
stdout
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Standard output is empty
https://ideone.com/FRmEwn
language:
C++ (gcc 8.3)
created:
6 years ago
visibility:
public

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