CODEWITHSUNDEEP
c++validationinput
Singh
Singh

Reputation: 229

Why for the same input in this C++ program it is giving two different results

Given below is a C++ program to find the value of x and y in simultaneous linear equations. 

using namespace std;
#include<iostream>
int main()
{
    int m,n,a,b,c,p,q,r,x,y;
    cout<<"For the system of equation ax+by=c and px+qy=r,";
    cout<<"\nGive the value of a,b,c,p,q and r respectively:";
    cin>>a>>b>>c>>p>>q>>r;
    m=q-((p*b)/a);
    n=r-((p*c)/a);
    if(q==0)
        cout<<"No solution";
    else
        y=(n/m);
    x=(c-(b*y))/a;
    cout<<"x= "<<x<<" & y= "<<y<<"\n";
    return 0;
}

The problem with this program is that when I am giving the inputs as

3 1 13 1 6 -7 I get x=4 & y=-1

That is

For the system of equation ax+by=c and px+qy=r,
Give the value of a,b,c,p,q and r respectively:3 1 13 1 6 -7
x= 4 & y= -1

Now again I am giving the same input but in a little different way

1 6 -7 3 1 13 I get x=5 & y=-2

That is

For the system of equation ax+by=c and px+qy=r,
Give the value of a,b,c,p,q and r respectively:1 6 -7 3 1 13
x= 5 & y= -2

The right answer is x= 5 & y= -2.

Now the question is that, we have two equations and we have to solve for x and y. Here it will not matter that by which method we solve these equation because by any method we will get the value of x and y as 5 and -2 respectively.

So for same two equations why I am getting two different solutions.

Kindly help me in understanding the problem in my program.

Upvotes: 0

Views: 291

Answers (1)

Blutkoete
Blutkoete

Reputation: 418

You are using the int type to store your variables. In the first case, a is 3, which leads to fractions in your equations which are cut off because int cannot store them.

In the second example, a is 1, so no fractions occur and your program calculates the correct answer.

Use float or double.

Upvotes: 2

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