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Program to read a Linear System of Equations,then evaluate it by using Gauss-Elimination Method and show the result

Posted By: Easy Tutor     Category: C++ Programming     Views: 3912

A C++ Program to read a Linear System of Equations,then evaluate it by using LU-Decomposition Method and show the result.

Code for Program to read a Linear System of Equations,then evaluate it by using Gauss-Elimination Method and show the result in C++ Programming

 # include <iostream.h>
 # include   <stdlib.h>
 # include    <stdio.h>
 # include    <conio.h>
 # include     <math.h>

 constint max_size=5;

 int n=0;

 char Row_interchanging=NULL;

 longdouble A[max_size][max_size]={0};
 longdouble L[max_size][max_size]={0};
 longdouble U[max_size][max_size]={0};
 longdouble X[max_size]={0};

 void show_screen( );
 void clear_screen( );
 void get_size_of_linear_equations( );
 void show_input(constint,constint,constint=0);
 void get_input_linear_equation( );
 void show_AB_matrices( );
 void make_first_row_largest( );
 void initialize_LU_matrices( );
 void apply_LU_decomposition_method( );
 void interchange_rows(constint,constint);
 void show_LU_matrices( );
 void generate_result( );
 void show_result( );

 int main( )
    {
       clrscr( );
       textmode(C4350);

       show_screen( );
       get_size_of_linear_equations( );
       get_input_linear_equation( );
       show_AB_matrices( );
       apply_LU_decomposition_method( );
       show_LU_matrices( );
       generate_result( );
       show_result( );

       getch( );
       return 0;
    }

 /*************************************************************************///--------------------------  show_screen( )  ---------------------------///*************************************************************************/void show_screen( )
    {
       cprintf("\n********************************************************************************");
       cprintf("*************************-                           -**************************");
       cprintf("*------------------------- ");

       textbackground(1);
       cprintf(" LU-Decomposition Method ");
       textbackground(8);

       cprintf(" --------------------------*");
       cprintf("*-***********************-                           -************************-*");
       cprintf("*-****************************************************************************-*");

       for(int count=0;count<42;count++)
      cprintf("*-*                                                                          *-*");

       gotoxy(1,46);
       cprintf("*-****************************************************************************-*");
       cprintf("*------------------------------------------------------------------------------*");
       cprintf("********************************************************************************");

       gotoxy(1,2);
    }

 /*************************************************************************///-------------------------  clear_screen( )  ---------------------------///*************************************************************************/void clear_screen( )
    {
       for(int count=0;count<37;count++)
      {
         gotoxy(5,8+count);
         cout<<"                                                                        ";
      }

       gotoxy(1,2);
    }

 /*************************************************************************///------------------  get_size_of_linear_equations( )  ------------------///*************************************************************************/void get_size_of_linear_equations( )
    {
       do
      {
         clear_screen( );

         gotoxy(44,11);
         cout<<"[ Maximum size = 4 ]";

         gotoxy(6,9);
         cout<<"Enter the size of the System of Linear Equations = n = ";

         cin>>n;

         if(n<=0 || n>max_size)
        {
           gotoxy(12,25);
           cout<<"Error : Wrong Input. Press <Esc> to exit or any other key";

           gotoxy(12,26);
           cout<<"        to try again.";

           n=int(getche( ));

           if(n==27)
              exit(0);
        }
      }
       while(n<=0 || n>max_size);

       gotoxy(6,15);
       cout<<"Do you want to use Row Interchanging Technique : (Y/N) ? : ";

       cin>>Row_interchanging;


       gotoxy(1,2);
    }

 /*************************************************************************///-------------  show_input(const int,const int,const int)  -------------///*************************************************************************/void show_input(constint x,constint y,constint y_cord)
    {
       int counter=0;
       int number_of_inputs=((x*n)+y+x);

       for(int count_1=0;count_1<n;count_1++)
      {
         gotoxy(6,(17+(count_1*2)+y_cord));
         cout<<"                                                                      ";

         gotoxy(6,(17+(count_1*2)+y_cord));

         for(int count_2=0;count_2<=n;count_2++)
        {
           if(counter==(number_of_inputs+1))
              textbackground(12);

           else
              textbackground(8);

           if(count_2==n)
              gotoxy((wherex( )+5),(17+(count_1*2)+y_cord));

           gotoxy(wherex( ),(17+(count_1*2)+y_cord));
           cprintf("      ");

           if(count_2==n)
              gotoxy((wherex( )-5),(17+(count_1*2)+y_cord));

           gotoxy((wherex( )-6),(17+(count_1*2)+y_cord));

           if(counter<=number_of_inputs && counter!=-1)
              {
             if(count_2==n)
                {
                   cout<<"  =  ";
                   cout<<A[count_1][count_2];
                }

             elseif(count_2==0)
                cout<<A[count_1][count_2]<<" x"<<(count_2+1);

             else
                cout<<fabs(A[count_1][count_2])<<" x"<<(count_2+1);
              }

           elseif(count_2==n)
              cout<<"  =  b"<<(count_1+1);

           else
              cout<<"a"<<(count_1+1)<<(count_2+1)<<" x"<<(count_2+1);

           if(count_2<(n-1) && A[count_1][(count_2+1)]>=0)
              cout<<"  +  ";

           elseif(count_2<(n-1))
              cout<<"  -  ";

           counter++;
        }
      }
    }

 /*************************************************************************///--------------------  get_input_linear_equation( )  -------------------///*************************************************************************/void get_input_linear_equation( )
    {
       clear_screen( );

       gotoxy(5,9);
       cout<<"Size of the System of Linear Equations = n = "<<n;

       gotoxy(5,13);
       cout<<"System of Linear Equations :";

       gotoxy(5,14);
       cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

       show_input(0,-1);

       for(int count_1=0;count_1<n;count_1++)
      {
         for(int count_2=0;count_2<=n;count_2++)
        {
           gotoxy(5,35);
           cout<<"                                                                    ";

           gotoxy(5,35);

           if(count_2<n)
              cout<<"Enter the value of a"<<(count_1+1)<<(count_2+1)<<" =  ";

           else
              cout<<"Enter the value of b"<<(count_1+1)<<" =  ";

           cin>>A[count_1][count_2];

           show_input(count_1,count_2);
        }
      }
    }

 /*************************************************************************///------------------------  show_AB_matrices( )  ------------------------///*************************************************************************/void show_AB_matrices( )
    {
       clear_screen( );

       gotoxy(5,9);
       cout<<"Convertion of given System of Linear Equations into Matrix-A & Matrix-B";

       gotoxy(5,10);
       cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

       gotoxy(12,13);
       cout<<"ÚÄ";

       gotoxy((12+(n*14)),13);
       cout<<"Ä¿";

       gotoxy(12,14);
       cout<<"³";

       gotoxy((13+(n*14)),14);
       cout<<"³";

       if((n%2)==0)
      gotoxy(6,(14+((n/2)*2)));

       else
      gotoxy(6,(15+((n/2)*2)));

       cout<<"A  =";

       for(int count_1=0;count_1<n;count_1++)
      {
         gotoxy(12,(15+(count_1*2)));
         cout<<"³";

         gotoxy(12,(16+(count_1*2)));
         cout<<"³";

         for(int count_2=0;count_2<n;count_2++)
        {
           gotoxy(15+(count_2*14),(15+(count_1*2)));
           cout<<A[count_1][count_2];
        }

         gotoxy((13+(n*14)),(15+(count_1*2)));
         cout<<"³";

         gotoxy((13+(n*14)),((count_1*2)+16));
         cout<<"³";
      }

       gotoxy(12,(15+(count_1*2)));
       cout<<"ÀÄ";

       gotoxy((12+(n*14)),(15+(count_1*2)));
       cout<<"ÄÙ";

       gotoxy(12,(20+(count_1*2)));
       cout<<"ÚÄ";

       gotoxy(26,(20+(count_1*2)));
       cout<<"Ä¿";

       gotoxy(12,(21+(count_1*2)));
       cout<<"³";

       gotoxy(27,(21+(count_1*2)));
       cout<<"³";

       gotoxy(6,(18+(count_1*2)+(n*2)));

       if((n%2)==0)
      gotoxy(6,(21+(count_1*2)+((n/2)*2)));

       else
      gotoxy(6,(22+(count_1*2)+((n/2)*2)));

       cout<<"B  =";

       for(int count_3=0;count_3<n;count_3++)
      {
         gotoxy(12,((22+(count_1*2))+(count_3*2)));
         cout<<"³";

         gotoxy(12,((23+(count_1*2))+(count_3*2)));
         cout<<"³";

         gotoxy(15,((22+(count_1*2))+(count_3*2)));
         cout<<A[count_3][n];

         gotoxy(27,((22+(count_1*2))+(count_3*2)));
         cout<<"³";

         gotoxy(27,((23+(count_1*2))+(count_3*2)));
         cout<<"³";
      }

       gotoxy(12,((22+(count_1*2))+(count_3*2)));
       cout<<"ÀÄ";

       gotoxy(26,((22+(count_1*2))+(count_3*2)));
       cout<<"ÄÙ";

       gotoxy(25,43);
       cout<<"Press any key to continue...";

       getch( );
    }

 /*************************************************************************///----------------------  make_first_row_largest( )  --------------------///*************************************************************************/void make_first_row_largest( )
    {
       int max_row_number=0;

       for(int count_1=0;count_1<n;count_1++)
      {
         if(fabs(A[max_row_number][0])<fabs(A[count_1][0]))
        max_row_number=count_1;
      }

       if(max_row_number>0)
      {
         longdouble temp[(max_size+1)]={0};

         for(int count_2=0;count_2<=n;count_2++)
        temp[count_2]=A[0][count_2];

         for(int count_3=0;count_3<=n;count_3++)
        A[0][count_3]=A[max_row_number][count_3];

         for(int count_4=0;count_4<=n;count_4++)
        A[max_row_number][count_4]=temp[count_4];
      }
    }

 /*************************************************************************///----------------------  initialize_LU_matrices( )  --------------------///*************************************************************************/void initialize_LU_matrices( )
    {
       for(int count_1=0;count_1<n;count_1++)
      {
         L[count_1][count_1]=1;
         L[count_1][n]=A[count_1][n];
      }

       for(int count_2=1;count_2<n;count_2++)
      L[count_2][0]=(A[count_2][0]/A[0][0]);

       for(int count_3=0;count_3<n;count_3++)
      U[0][count_3]=A[0][count_3];
    }

 /*************************************************************************///------------------  apply_LU_decomposition_method( )  -----------------///*************************************************************************/void apply_LU_decomposition_method( )
    {
       if(Row_interchanging=='Y' || Row_interchanging=='y')
      make_first_row_largest( );

       initialize_LU_matrices( );

       for(int count_1=0;count_1<(n-1);count_1++)
      {
         longdouble options[max_size]={0};

         int option_number=0;

         for(int count_2=(count_1+1);count_2<n;count_2++)
        {
           for(int count_3=0;count_3<n;count_3++)
              options[option_number]+=(L[count_2][count_3]*U[count_3][(count_1+1)]);

           options[option_number]=(A[count_2][(count_1+1)]-options[option_number]);
           option_number++;
        }

         int max_row_number=0;

         for(int count_4=0;count_4<option_number;count_4++)
        {
           if(fabs(options[max_row_number])<=fabs(options[count_4]))
              {
             if(fabs(options[max_row_number])==fabs(options[count_4]) &&
                   options[max_row_number]!=options[count_4])
               {
                  if(options[max_row_number]<options[count_4])
                 max_row_number=count_4;
               }

             else
                max_row_number=count_4;
              }
        }

         if(max_row_number>0 && (Row_interchanging=='Y' || Row_interchanging=='y'))
        interchange_rows((count_1+1),(count_1+1+max_row_number));

         U[(count_1+1)][(count_1+1)]=options[max_row_number];

         longdouble temp=0;

         for(int count_5=(count_1+2);count_5<n;count_5++)
        {
           for(int count_6=0;count_6<n;count_6++)
              temp+=(L[count_5][count_6]*U[count_6][(count_1+1)]);

           temp=A[count_5][(count_1+1)]-temp;
           temp/=U[(count_1+1)][(count_1+1)];

           L[count_5][(count_1+1)]=temp;
           temp=0;

           for(int count_7=0;count_7<n;count_7++)
              temp+=(L[(count_1+1)][count_7]*U[count_7][count_5]);

           temp=A[(count_1+1)][count_5]-temp;
           U[(count_1+1)][count_5]=temp;
           temp=0;
        }
      }
    }

 /*************************************************************************///---------------  interchange_rows(const int,const int)  ---------------///*************************************************************************/void interchange_rows(constint row_1,constint row_2)
    {
       longdouble temp_A[max_size]={0};

       for(int count_1=0;count_1<=n;count_1++)
      temp_A[count_1]=A[row_1][count_1];

       for(int count_2=0;count_2<=n;count_2++)
      A[row_1][count_2]=A[row_2][count_2];

       for(int count_3=0;count_3<=n;count_3++)
      A[row_2][count_3]=temp_A[count_3];

       longdouble temp_L0=L[row_1][0];
       longdouble temp_Ln=L[row_1][n];

       L[row_1][0]=L[row_2][0];
       L[row_2][0]=temp_L0;

       L[row_1][n]=L[row_2][n];
       L[row_2][n]=temp_Ln;
    }

 /*************************************************************************///------------------------  generate_result( )  -------------------------///*************************************************************************/void generate_result( )
    {
       for(int count_1=0;count_1<n;count_1++)
      {
         U[count_1][n]=L[count_1][n];

         for(int count_2=0;count_2<count_1;count_2++)
        L[count_1][count_2]=(L[count_1][count_2]*U[count_2][n]);

         for(int count_3=0;count_3<count_1;count_3++)
        U[count_1][n]-=L[count_1][count_3];

         U[count_1][n]/=L[count_1][count_1];
      }

       for(int count_4=(n-1);count_4>=0;count_4--)
      {
         X[count_4]=U[count_4][n];

         for(int count_5=(n-1);count_5>count_4;count_5--)
        U[count_4][count_5]=(U[count_4][count_5]*X[count_5]);

         for(int count_6=(n-1);count_6>count_4;count_6--)
        X[count_4]-=U[count_4][count_6];

         X[count_4]/=U[count_4][count_4];
      }
    }

 /*************************************************************************///------------------------  show_LU_matrices( )  ------------------------///*************************************************************************/void show_LU_matrices( )
    {
       clear_screen( );

       gotoxy(6,9);
       cout<<"Decomposition of Matrix-A into Matrix-L and Matrix-U :";

       gotoxy(6,10);
       cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

       for(int count_1=1;count_1<=2;count_1++)
      {
         gotoxy(12,((count_1*15)-2));
         cout<<"ÚÄ";

         gotoxy((12+(n*14)),((count_1*15)-2));
         cout<<"Ä¿";

         gotoxy(12,((count_1*15)-1));
         cout<<"³";

         gotoxy((13+(n*14)),((count_1*15)-1));
         cout<<"³";

         if((n%2)==0)
        gotoxy(6,((count_1*15)+((n/2)*2)-1));

         else
        gotoxy(6,((count_1*15)+((n/2)*2)));

         if(count_1==1)
        cout<<"L  =";

         elseif(count_1==2)
        cout<<"U  =";

         for(int count_2=0;count_2<n;count_2++)
        {
           gotoxy(12,((count_1*15)+(count_2*2)));
           cout<<"³";

           gotoxy(12,((count_1*15)+(count_2*2)+1));
           cout<<"³";

           for(int count_3=0;count_3<n;count_3++)
              {
             gotoxy(15+(count_3*14),((count_1*15)+(count_2*2)));

             if(count_1==1)
                cout<<L[count_2][count_3];

             elseif(count_1==2)
                cout<<U[count_2][count_3];
              }

           gotoxy((13+(n*14)),((count_1*15)+(count_2*2)));
           cout<<"³";

           gotoxy((13+(n*14)),((count_1*15)+(count_2*2)+1));
           cout<<"³";
        }

         gotoxy(12,((count_1*15)+(count_2*2)));
         cout<<"ÀÄ";

         gotoxy((12+(n*14)),((count_1*15)+(count_2*2)));
         cout<<"ÄÙ";
      }

       gotoxy(25,43);
       cout<<"Press any key to continue...";

       getch( );
    }

 /*************************************************************************///-----------------------------  show_result( )  ------------------------///*************************************************************************/void show_result( )
    {
       clear_screen( );

       gotoxy(6,10);
       cout<<"Given System of Linear Equations :";

       gotoxy(6,11);
       cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

       show_input((n-1),n,-4);

       gotoxy(6,26);
       cout<<"Result of given System of Linear Equations :";

       gotoxy(6,27);
       cout<<"ÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍÍ";

       for(int count=0;count<n;count++)
      {
         gotoxy(10,(29+count+count));
         cout<<"x"<<(count+1)<<" = "<<X[count];
      }

       gotoxy(6,41);
       cout<<"Note : The given system of Linear Equations is solved by using";

       gotoxy(6,43);
       cout<<"       Do-Little Method";

       gotoxy(30,43);

       if(Row_interchanging=='Y' || Row_interchanging=='y')
      cout<<"and Row-Interchanging Method.";

       else
      cout<<".";

       gotoxy(1,2);
    }
  
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Easy Tutor
Easy Tutor author of Program to read a Linear System of Equations,then evaluate it by using Gauss-Elimination Method and show the result is from United States. Easy Tutor says

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