Matrix Determination Issue in getting hidden inputs

We had given a code ro write an Octave code to find the product of two matrices A and B, element-wise, and then reverse the rows.

Print them, and then find the determinant of the resulting matrix. Below is one of custom inputs which are visible to us, rest does not.

3

3

1 2 3

2 3 4

1 3 5

2 3 4

1 3 5

4 5 6

Sample Output:

Reversed_Matrix = 4 15 30

2 9 20

2 6 12

Determinant = 12

The first and second row denote the dimensions of the first and second square matrices. The next three rows denote the values in the first matrix, and the last three rows denote the values of the next matrix.

We written code as below which is correct, but we do not want it to be hard coded value, it pull it from custom input as mentioned above, please help how to remove value input as hard coded i.e. value which we providing in Reversed_Matrix. This we asking because we have 4 test case. For 1 we can see input, hence as per it we developed code, for rest 3 were not know what will be input hence do not want not any hard code input.

We are getting same output for test 1 but other 3 hidden test cases failled.

function matr()
     Reversed_Matrix= flip([1 2 3; 2 3 4 ; 1 3 5].* [2 3 4; 1 3 5; 4 5 6])
     Determinant= det(Reversed_Matrix)
endfunction
matr()

[Stephen23]

https://web.archive.org/web/20200817032413/https://www.mathworks.com/matlabcentral/answers/580263-matrix-determination-issue-in-getting-hidden-inputs

Answer 1

[Sara Boznik]

function matr()
if [n,n]==size(A) & [m,m]=size(B) & n==m
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
sol=det(Reversed_Matrix)
else fprintf('Determinant does not exists.')
end
endfunction
n=input('n')
m=input('m')
A=input('A');
B=input('B');
matr()

[Ashish Jindal]

We getting below error-

• parse error near line 2 of file /tmp/submission/20200816/17/31/hackerrank-38209e8fdf1cc7164856f342f6789d07/code/Solution.octave
• invalid left hand side of assignment
• >>> if [n,n]==size(A) & [m,m]=size(B) & n==m
• ^
• error: source: error sourcing file '/tmp/submission/20200816/17/31/hackerrank-38209e8fdf1cc7164856f342f6789d07/code/Solution.octave'

In other istance same issue

Error(s), warning(s):

parse error near line 3 of file 611546326/source_rextester.m invalid left hand side of assignment >>> if [n,n]==size(A) & [m,m]=size(B) & n==m ^ error: source: error sourcing file '611546326/source_rextester.m'

[Ashish Jindal]

We had corrected code now getting below issue

function matr()
if [n,n]==size(A) & [m,m]==size(B) & n==m
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
sol=det(Reversed_Matrix)
else fprintf('Determinant does not exists.')
end
endfunction
n=input('n');
m=input('m';)
A=input('A');
B=input('B');
matr()

Error is

• parse error:
• syntax error
• >>> 1 2 3
• ^
• error: called from
• Solution.octave at line 15 column 2

[Sara Boznik]

Did you put input in?

[Ashish Jindal]

yes, it is as

3

3

1 2 3

2 3 4

1 3 5

2 3 4

1 3 5

4 5 6

[Ashish Jindal]

Seems we need to do below thing which will fetch some output which will nto match as what expect but code need to work if below direction, which need further modification

function matr()
n=input("");
m=input("");
A=rand(n);
B=rand(m);
if [n,n]==size(A) & [m,m]==size(B) & n==m
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
Determinant= det(Reversed_Matrix)
else fprintf('Determinant does not exists.')
end
endfunction
matr()

Here out will be like

Reversed_Matrix =

0.634078 0.398280 0.120195

0.790813 0.083681 0.334776

0.164293 0.095670 0.069930

Determinant = -0.0092764

Somehow we need to input customer input here.

[Sara Boznik]

yes this is for random n and m

Did you put matrix like: [1 2 3; 4 5 6 ...]?

[Ashish Jindal]

See as told earlier we have 5 test cases, we can see what system will input other we cannot. For which we can see input is as

3

3

1 2 3

2 3 4

1 3 5

2 3 4

1 3 5

4 5 6

Our condition is that from above input we need to prepare A and B matrix. Here condition is The first and second row denote the dimensions of the first and second square matrices. The next three rows denote the values in the first matrix, and the last three rows denote the values of the next matrix. If fist row is 3 and second row is 3 then next 3 will be value for A and after whcih next 3 will value for B. Here it is possible then in hidden case ist row shows as 2 , second as 2 then next 2 row will be matrix for A and next 2 will be for B. Simillarly row 1 can be 4 and second can be 4 also. Then next 4 rows will be matrix for A and next 4 will be for B. Like

2

2

1 2

2 3

2 3

1 3

4

4

1 2 3 1

2 3 4 0

1 3 5 8

1 2 3 1

2 3 4 1

1 3 5 3

4 5 6 5

1 2 3 7

We will not able to see this input, so we need to prepare will we run code it automatically prepare matrix A and B as per hidden inputs and we get desire results.

[Sara Boznik]

Do you have load this input from file?

[Ashish Jindal]

No.. plz see screen show where we doing testing. There is only 1 place where we write code. It automatically ececute all test cases. We just need to write code and execute it. We cannot provide any input for it.

[Sara Boznik]

That is the last idea which I have it:

hiddeninputs=load('dataname.txt')
n=hiddeninputs(1,1)
m=hiddeninputs(2,1)
if n==m
    for i=1:n
        A=hiddeninputs(n+1+i,i)
        B=hiddeninputs(2*n+1+i,i)
    end
end
if [n,n]==size(A) & [m,m]=size(B) & n==m
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
sol=det(Reversed_Matrix)
else fprintf('Determinant does not exists.')
end

[Ashish Jindal]

not working :-(

[Sara Boznik]

Sorry, I tried my best. I still do not understand what you have to do. I taught that the task is that you see the input and you have to get determinant and reverse matrix. But you said that you can see only 1 input, so I do not understand how you will get output without knowing what is input :(

Good luck.

[Ashish Jindal]

Please review below code, we think we can try it but some issue in it

function matr()
x = scanf("%d", "C");
y = scanf("%d", "C");
for i=1:5
    x(i) = scanf("%d", "C");
end
for j=1:5
    y(j) = scanf("%d", "C");
end
for i=1:3
    for j=1:2
        A = scanf("%d", "C");
    end
end
for i=1:3
    for j=1:2
        B = scanf("%d", "C");
    end
end
n=x;
m=y;
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
Determinant= det(Reversed_Matrix)
endfunction
matr()

[Ashish Jindal]

New code is

function matr()
x = scanf("%d", "C");
y = scanf("%d", "C");
for i=1:x
for j=1:x
A = scanf("%d", "C");
printf("%d", A);   
end
end
for i=1:y 
for j=1:y
B = scanf("%d", "C");
printf("%d", B);
end
end
A
B
endfunction
matr()

Here output is as

123234135

234135456

5

6

Hence if we determinate then i is coming as 30, might be some slight issue in code

[Sara Boznik]

Did you get A and B as vector?

My Matlab does not know function scanf, what is function for?

[Ashish Jindal]

Here A value is 123234135

Here B value is 234135456

This via printf

In outside loop

A = 5

B = 6

[Ashish Jindal]

scanf is used to scan custom user input. Here how we can convert value of A and B in vecotr?

[Sara Boznik]

Outside the loop you just get only the last number. You have to save A like matrix nxn that you can get the right determinant. You need A and B like matrix not vector.

My suggestion is:

function matr()
x = scanf("%d", "C"); %%Is that size of matrix?
y = scanf("%d", "C");
for i=1:x
for j=1:x
A = scanf("%d", "C");
AA=zeros(x,x) %%with zeros you can define the dimension of AA
AA(i,j)=A(i,j) %%this should change the same position elements in AA with values from A
end
end
for i=1:y 
for j=1:y
B = scanf("%d", "C");
BB=zeros(y,y)
BB(i,j)=B(i,j)
end
end
endfunction
matr()

[Ashish Jindal]

How we will define reverse matrix and determination then?

[Ashish Jindal]

x = scanf("%d", "C"); %%Is that size of matrix?

Here value of x will be just 3. It is not size.

• error: A(_,2): but A has size 1x1
• error: called from
• matr at line 8 column 8
• Solution.octave at line 20 column 1

[Ashish Jindal]

function matr()
x = scanf("%d", "C");
y = scanf("%d", "C");
for i=1:x
for j=1:x
A = scanf("%d", "C");
[x,x]=size(A);
AA=zeros(x,x) 
AA(i,j)=A(i,j) 
end
end
for i=1:y 
for j=1:y
B = scanf("%d", "C");
[y,y]=size(B);
BB=zeros(y,y)
BB(i,j)=B(i,j)
end
end
endfunction

Can we do it?

[Sara Boznik]

Reverse matrix and determinant you get the same like before but as I understand you right first you have to get matrix A and B?

Ok, so x define size if x=3, dimension of matrix is 3x3.

How A is size 1x1 if you defined that x=3?

Maybe you can try only AA(i,j)=A.

[Ashish Jindal]

Written as

function matr()
x = scanf("%d", "C");
y = scanf("%d", "C");
for i=1:x
for j=1:x
A = scanf("%d", "C");
AA=zeros(x,x) ;
AA(i,j)=A
end
end
for i=1:y 
for j=1:y
B = scanf("%d", "C");
BB=zeros(y,y);
BB(i,j)=B
end
end   
endfunction
matr()

Output as

• AA =
• 1 0 0
• 0 0 0
• 0 0 0
• AA =
• 0 2 0
• 0 0 0
• 0 0 0
• AA =
• 0 0 3
• 0 0 0
• 0 0 0
• AA =
• 0 0 0
• 2 0 0
• 0 0 0
• AA =
• 0 0 0
• 0 3 0
• 0 0 0
• AA =
• 0 0 0
• 0 0 4
• 0 0 0
• AA =
• 0 0 0
• 0 0 0
• 1 0 0
• AA =
• 0 0 0
• 0 0 0
• 0 3 0
• AA =
• 0 0 0
• 0 0 0
• 0 0 5
• BB =
• 2 0 0
• 0 0 0
• 0 0 0
• BB =
• 0 3 0
• 0 0 0
• 0 0 0
• BB =
• 0 0 4
• 0 0 0
• 0 0 0
• BB =
• 0 0 0
• 1 0 0
• 0 0 0
• BB =
• 0 0 0
• 0 3 0
• 0 0 0
• BB =
• 0 0 0
• 0 0 5
• 0 0 0
• BB =
• 0 0 0
• 0 0 0
• 4 0 0
• BB =
• 0 0 0
• 0 0 0
• 0 5 0
• BB =
• 0 0 0
• 0 0 0
• 0 0 6

[Sara Boznik]

Ok, thats look fine, we just have to remember how to save previous matrix.

Maybe the solution is that you delete zeros and write only:

AA(i,j)=A

[Ashish Jindal]

We written as

function matr()
x = scanf("%d", "C");
y = scanf("%d", "C");
for i=1:x
for j=1:x
A = scanf("%d", "C");
AA(i,j)=A
end
end
for i=1:y 
for j=1:y
B = scanf("%d", "C");
BB(i,j)=B
end
end   
endfunction
matr()

Output as

• AA = 1
• AA =
• 1 2
• AA =
• 1 2 3
• AA =
• 1 2 3
• 2 0 0
• AA =
• 1 2 3
• 2 3 0
• AA =
• 1 2 3
• 2 3 4
• AA =
• 1 2 3
• 2 3 4
• 1 0 0
• AA =
• 1 2 3
• 2 3 4
• 1 3 0
• AA =
• 1 2 3
• 2 3 4
• 1 3 5
• BB = 2
• BB =
• 2 3
• BB =
• 2 3 4
• BB =
• 2 3 4
• 1 0 0
• BB =
• 2 3 4
• 1 3 0
• BB =
• 2 3 4
• 1 3 5
• BB =
• 2 3 4
• 1 3 5
• 4 0 0
• BB =
• 2 3 4
• 1 3 5
• 4 5 0
• BB =
• 2 3 4
• 1 3 5
• 4 5 6

[Ashish Jindal]

Thanks a lot issue resolved, final code is

function matr()
x = scanf("%d", "C");
y = scanf("%d", "C");
for i=1:x
for j=1:x
A = scanf("%d", "C");
AA(i,j)=A;
end
end
for i=1:y 
for j=1:y
B = scanf("%d", "C");
BB(i,j)=B;
end
end   
E=AA.*BB;
Reversed_Matrix=flip(E)
Determinant= det(Reversed_Matrix)
endfunction
matr()

[Sara Boznik]

Sorry that it tooks so long, but I am happy that finally works fine.

Best of luck.

[Ashish Jindal]

Not to sorry this was a tricky question need collaboartion from both sidee.

Thanks a lot...

[Senthilkumar Ramani]

Try this code.

function matr()

# Enter code. Read input from STDIN. Print output to STDOUT.

x = scanf("%d", "C");

y = scanf("%d", "C");

for i=1:x

for j=1:x

A = scanf("%d", "C");

AA(i,j)=A;

end

end

for i=1:y

for j=1:y

B = scanf("%d", "C");

BB(i,j)=B;

end

end

disp("Reversed_Matrix =\n"), disp(flip(AA .* BB));

printf("\nDeterminant = %d", det(flip(AA .* BB))), printf("\n");

endfunction

matr()

Answer 2

[KSSV]

function Determinant = matr(A,B)
     Reversed_Matrix= flip(A.* B) ; 
     Determinant= det(Reversed_Matrix) ; 
end

Save the above function. Now define the matrices A and B call the function

val = matr(A,B) ; 

Answer 3

[Sara Boznik]

In function you write:

function Determinant = matr (A,B)
Reversed_Matrix=flip(A.*B);
Determinant=det(Reversed_Matrix);
end

In script you write:

A=input('Write your first matrix:')
B=input('Write your second matrix:')
determinant=matr(A,B)

Best of luck.

[Ashish Jindal]

Here we have 4 test cases.... for 1 test case we see input as

3

1 2 3

2 3 4

1 3 5

2 3 4

1 3 5

4 5 6

This mean as the first and second row denote the dimensions of the first and second square matrices. The next three rows denote the values in the first matrix, and the last three rows denote the values of the next matrix.

For next 3 we have hidden input which we cannot see. Also we need to write code in, which is also fixed.

function matr()
   Write your code here
endfunction
matr()

[Ashish Jindal]

[Ashish Jindal]

Here code is bit tricky might be some pre determinent code hence facing issue how to resolve that

[Ashish Jindal]

We did following thing for just checking purpose to see what is in hidden data -

function matr()
     x=input("");
     y=input("");
     printf("%d\n", x);
     printf("%d\n", y);
     Reversed_Matrix= flip([1 2 3; 2 3 4 ; 1 3 5].* [2 3 4; 1 3 5; 4 5 6])
     Determinant= det(Reversed_Matrix)
endfunction
matr()

We found for 0 and 1 cases it is

3

3

For 2 and 3 it is

2

2

For 4 it is

4

4

So, here we have 3*3, 2*2 and 4*4. We seems need to prepare matrix like it. So basically we need to know what we need to give in plce of ? in below code we think so.

function matr()
     x=input("");
     y=input("");
     A= ? ;
     B= ? ;
     Reversed_Matrix= flip(A.* B)
     Determinant= det(Reversed_Matrix)
endfunction
matr()

[Sara Boznik]

Hi! My english is quite bad but if I understand you right you have cases with different dimension of matrix? If you just have different dimension is this not important for matlab code.

Or maybe do you need this:

function Determinant = matr (A,B)
[n,n]=size(A)
[m,m]=size(B)
C=zeros(n,n)
D=zeros(m,m)
C=A
D=B
E=C.*D
Reversed_Matrix=flip(E);
Determinant=det(Reversed_Matrix);
end

[Ashish Jindal]

We are almots near but still someting mssing, when we written code as

function matr()
     x=input("");
     y=input("");
     A=zeros(x,x);
     B=zeros(y,y);
     Reversed_Matrix= flip(A.* B)
     Determinant= det(Reversed_Matrix)
endfunction
matr()

We getting output as -

• Reversed_Matrix =
• 0 0 0
• 0 0 0
• 0 0 0
• Determinant = 0

It should be as

• Reversed_Matrix =
• 4 15 30
• 2 9 20
• 2 6 12
• Determinant = 12

[Sara Boznik]

A=input('A')
B=input('B')
[n,n]=size(A)
[m,m]=size(B)
C=zeros(n,n)
D=zeros(m,m)
C=A
D=B
E=C.*D
Reversed_Matrix=flip(E)
sol=det(Reversed_Matrix)

Attached you have a screenshot of my output, so I think it works fine.

Best of luck.

[Ashish Jindal]

We written code as

function matr()
n=input("");
m=input("");
A=input('A');
B=input('B');
[n,n]=size(A);
[m,m]=size(B);
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
Determinant= det(Reversed_Matrix)
endfunction
matr()

getting error as

Compiler Message

Runtime Error

Error (stderr)

• parse error:
• syntax error
• >>> 1 2 3
• ^
• error: called from
• matr at line 4 column 2
• Solution.octave at line 17 column 1

[Sara Boznik]

n=input("");
m=input("");
A=input('A');
B=input('B');

This part should be written in script not in function, than also in scripr you call the function.

And for end of function you should write only end, not endfunction.

[Ashish Jindal]

We written as

n=input("");
m=input("");
A=input('A');
B=input('B');
function matr()
[n,n]=size(A);
[m,m]=size(B);
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
Determinant= det(Reversed_Matrix)
endfunction
matr()

Same issue

[Ashish Jindal]

Our input is like dis

3

3

1 2 3

2 3 4

1 3 5

2 3 4

1 3 5

4 5 6

So, it easily take value for m and n as 3 respectively. But issue is that we think we need to covert

1 2 3

2 3 4

1 3 5

to A matrix, this can be as

1 2 3

2 3 4

If n = 2

Simillarly if m = 3 we need to convert below into B matrix -

2 3 4

1 3 5

4 5 6

if M = 2 then

2 3 4

1 3 5

[Sara Boznik]

You need matrix n*n that you can have determinant.

If you don't have same dimension of matrix determinant not exist. You have to have SQUARE MATRIX.

https://people.richland.edu/james/lecture/m116/matrices/determinant.html

Answer 4

[Sara Boznik]

Script:

% n=input(""); that part is actually no needed
% m=input("");
A=input('A');
B=input('B');
matr(A,B)

Function:

function [Reversed_Matrix, Determinant] = matr(A,B)
[n,n]=size(A);
[m,m]=size(B);
C=zeros(n,n);
D=zeros(m,m);
C=A;
D=B;
E=C.*D;
Reversed_Matrix=flip(E)
Determinant= det(Reversed_Matrix)
end

Also you have attached it.

[Ashish Jindal]

Here we have lot of constant value like below thing

function matr()
   Write your code here
endfunction
matr()

We cannot change function, what ever we need to do need to write in that function only i.e. in "Write your code here".

[KSSV]

You straight away copy your matrix as you did in the first test case.

[Sara Boznik]

Is that something for school?

Than I will write only the function.

[Ashish Jindal]

See we have 5 test cases as we mentioned above... we can see matrix input for 1 case only rest is hidden. Please see our screen shots.

Our task is to write code in below

function matr()
   Write your code here
endfunction
matr()

We cannot change function, what ever we need to do need to write in that function only i.e. in "Write your code here".

Hidden test case automatically runs.

We had another test case where 1 test case was visble rest not. We passed it.

function fibo(n)
    fib=zeros(1,n);
    fib(1)=1;
    fib(2)=1;
    k=3;
    while k <= n
    fib(k)=fib(k-2)+fib(k-1);
    k=k+1;
    endwhile
    if (n>1)
    fprintf("Fibonacci series: ");
    fprintf('%g ',fib);
    endif
endfunction
a = input("");
fibo(a)

Here is simillar 1 case input we can see rest we cannot. Inital code for this was as

function fibo(n)
    "Write your code here"
endfunction
a = input("");
fibo(a)

We written code in "Write your code here", Which work perfectly. Simillar for this case also we need to write code in same place without touching funtion part.

Answer 5

[Senthilkumar Ramani]

This code is working perfectly.

function matr()

x = scanf("%d", "C");

y = scanf("%d", "C");

for i=1:x

for j=1:x

A = scanf("%d", "C");

AA(i,j)=A;

end

end

for i=1:y

for j=1:y

B = scanf("%d", "C");

BB(i,j)=B;

end

end

disp("Reversed_Matrix="), disp(flip(AA .* BB));

printf("Determinant=%d", det(flip(AA .* BB))), printf("\n");

endfunction

matr()