Why when I run the program twice it prints different answers for one input؟

Question

1.80/5 (2 votes)

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For the domajhuli function, when I give an input, it prints the correct answer, but the second time, it prints something else for the same input.

Please tell me what the problem is?

What I have tried:

#include <iostream>
#include <cmath>
#define Size 3
#define N 2
using namespace std;


void semajholi();
float determinan( float matrix[Size][Size], int n) ;
void domajholi();

int main()
{
    int c;
    cout<<"che moadelei hal konam 2/3 majholi ? "<<endl;
      cin>>c;


      switch(c)
      {
          case 2:
           domajholi();
            break;
          case 3:
          semajholi();
           break;
      }

}

 void semajholi()
 {

    char ch1 = 'x';
    char ch2 = 'y';
    char ch3 = 'z';

    float Mat[Size][Size];
    float Mat_m[Size];

    float mat_x[Size][Size];
    float mat_y[Size][Size];
    float mat_z[Size][Size];


      cout<<"zaraib ra vard kon : "<<endl;

       for(int i=0 ;i<Size;i++)
        for(int j=0;j<Size;j++)
          cin>>Mat[i][j];


       cout<<"malomat ra vared kon : "<<endl;
           for(int i=0 ;i<Size;i++)
            cin>>Mat_m[i];

            //tashkil matris majhulat

             for(int i=0 ;i<Size;i++)
             {
                 for(int j=0;j<Size;j++)
                 {
                     if(j==0)
                      mat_x[i][j]=Mat_m[i];
                     else
                      mat_x[i][j]=Mat[i][j];

                     if(j == 1)
                        mat_y[i][j]=Mat_m[i];
                     else
                       mat_y[i][j]=Mat[i][j];

                     if(j == 2)
                      mat_z[i][j]=Mat_m[i];
                     else
                      mat_z[i][j]=Mat[i][j];

                 }
             }
             //peyda kardan jvb

                float det  = determinan(Mat,Size);
                if(det != 0)
                {
                    float detx = determinan(mat_x,Size);
                    float dety = determinan(mat_y,Size);
                    float detz = determinan(mat_z,Size);

                    cout<<endl<<endl;

                    cout<<"jvb moadele : "<<endl;

                    cout<<ch1<<" = "<<detx/det<<endl;
                    cout<<ch2<<" = "<<dety/det<<endl;
                    cout<<ch3<<" = "<<detz/det<<endl;

                }

                else
                cout<<"jvb nadarad ."<<endl;
 }
float determinan( float matrix[Size][Size], int n)
{
    float det = 0;
    for(int i = 0; i < Size; i++)
		det +=  (matrix[0][i] * (matrix[1][(i+1)%3] * matrix[2][(i+2)%3] - matrix[1][(i+2)%3] * matrix[2][(i+1)%3]));

   return det;
}
void domajholi()
{
    
 int matzarb[2][2];
 int malom[2][1];
 int Zqtrasli = 1;
 int Zqtrfei  = 1;
 float  maxosdet;
 float varonmat[2][2];
 float jvb[2][1];
 float temp;
 float det;
///////////////////////////////////////////
    for(int i=1 ; i<=2 ; i++)
    {
        cout<<"Enter zaraib moadele " << i<<" : "<<endl;
          for(int j=1 ; j<=2 ; j++)
           cin>>matzarb[i][j];

    }
 /////////////////////////////////////////
    cout<<"Enter  malomat : "<<endl;
    for(int i=1 ; i<=2 ; i++)
       for(int j=1 ; j<=1 ; j++)
       {
        cout<<"("<<i<<","<<j<<") : ";
        cin>>malom[i][j];
       }
       cout<<endl<<endl;
///////////////////////////////////////////////
    for(int i=1 ; i<=2 ; i++)
       for(int j=1 ; j<=2 ; j++)
       {
           if(i==j)
          {
              Zqtrasli *= matzarb[i][j];
          }
          else
          {
              Zqtrfei *= matzarb[i][j];
          }
       }

       det = Zqtrasli - Zqtrfei;
       maxosdet = (1) / (det)  ;
       cout<<maxosdet<<endl;
///////////////////////////////////////////////////
     for(int i=1 ; i<=2 ; i++)
       for(int j=1 ; j<=2 ; j++)
       {
           if(i + j == 3)
           {
               matzarb[i][j] = (-1) * matzarb[i][j];
           }

          else if(i==1 && j==1)
          {
            temp = matzarb[i][j];
            matzarb[i][j]=matzarb[i+1][j+1];
            matzarb[i+1][j+1]=temp;
          }




           varonmat[i][j] = maxosdet * matzarb[i][j];
       }
///////////////////////////////////////////////////

for(int i=1 ; i<=2 ; i++)
       for(int j=1 ; j<=2 ; j++)
       {


           cout<<varonmat[i][j] <<endl;
       }
/////////////////////////////////////////////////////
    for(int i = 1; i<= 2; i++)
    for( int j = 1; j<= 1; j++)
        for(int k = 1; k<=2; k++)
        {
            jvb[i][j] += varonmat[i][k] * malom[k][j];
        }
 ////////////////////////////////////////////////////
    cout<<"jvb moadele :  "<<endl;
    cout<<"x = "<<jvb[1][1]<<endl;
    cout<<"y = "<<jvb[2][1]<<endl;


}

Posted 22-Jun-21 9:30am

urmiye city

Updated 24-Aug-21 1:55am

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Comments

Patrice T 22-Jun-21 15:40pm

What input ?

jeron1 22-Jun-21 16:13pm

One issue, in the domajholi() function, you declare

int matzarb[2][2];

then you do...
for(int i=1 ; i<=2 ; i++)
{
cout<<"Enter zaraib moadele " << i<<" : "<<endl;
for(int j= 1 ; j <=2 j++)
{
cin >> matzarb[i][j];
.
.
.
}

When i or j is equal to 2 you will have a problem. The only valid indexes here are 0 and 1. This type of thing is probably an issue in several places.

Joe Woodbury 24-Jun-21 1:44am

First, this is C++; declare variables just before using them (in the right scope).

Second, arrays are zero based, not one based.

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armagedescu · Answer 1 · 2021-08-24T01:55:00

Having a problem in this piece of code particularily and the same in some others of your loops:

C++

for(int i=1 ; i<=2 ; i++)
{
    cout<<"Enter zaraib moadele " << i<<" : "<<endl;
    for(int j=1 ; j<=2 ; j++)
       cin>>matzarb[i][j];

}

You are running out of ranges. C++ indexes are zero based, so in this piece of code you are running from index 2 to 3

Correct solution is to be zero based

C++

for(int i = 0 ; i < 2 ; i++) //see starting from 0 and condition < instead of <=
{
    //i + 1 means showing it as 1 based
    cout<<"Enter zaraib moadele " << (i + 1)<<" : "<<endl;
    for(int j = 0 ; j < 2 ; j++)
       cin>>matzarb[i][j];

}

Do it in all your loops.