Why do these lines of code not function properly?

In this function the first if statement does not work when I provide a matrix with elements larger than 4. I have tried using for loops but that effects the rest of the program for some reason. Also when elseif any(diff(sort(m(:,1))==0)) does in fact equal zero the out is not returned as zero but instead made into one. I spent hours trying to debug it, but I am still having issues. Any assistance is appreciated, thank you.

function out=issudoku(m)
[R,C]=size(m);

          if m()>4
              out=0;

          else if R~=4 || C~=4
              out=0;

%Find if any number on the board is not a 1, 2, 3 or 4

%%%see if any number is repeated within the individual squares
        elseif m(1,1)==m(2,1)||m(1,1)==m(1,2)||m(1,1)==m(2,2)
            out=0;
        elseif m(3,1)==m(4,1)||m(3,1)==m(3,2)||m(3,1)==m(4,2)
            out=0;
        elseif m(1,3)==m(2,3)||m(1,3)==m(1,4)||m(1,3)==m(2,4)
            out=0;
        elseif m(3,3)==m(4,3)||m(3,3)==m(3,4)||m(3,3)==m(4,4)
            out=0;

          %repeated numbers within columns:
          elseif  any(diff(sort(m(:,1))==0))
              out=0;
          elseif  any(diff(sort(m(:,2))==0))
              out=0;
          elseif  any(diff(sort(m(:,3))==0))
              out=0;
          elseif  any(diff(sort(m(:,4))==0))
              out=0;

          %repeated numbers within rows:
          elseif  any(diff(sort(m(1,:))==0))
              out=0;
          elseif  any(diff(sort(m(2,:))==0))
              out=0;
          elseif  any(diff(sort(m(3,:))==0))
              out=0;
          elseif  any(diff(sort(m(4,:))==0))
              out=0;

          else
             out=1;
              end
          end
  end

Answer 1

[Walter Roberson]

Perhaps you want

 if any(m>4)

??

[Mohannad Abboushi]

I tried that and it doesn't do anything at all

[Mohannad Abboushi]

I changed the code a bit and tried debugging it for why out does not become false when this matrix is provided: [1 4 2 3; 3 2 4 1; 1 4 3 2; 2 3 1 4]. The code seems valid, but it skips over the if statement when a~=validnumbers. What's going on??

function out=issudoku(m)
out=true;
validnumbers=[1,2,3,4];
[R,C]=size(m);

%check if sudoku board is 4x4
if R~=4||C~=4
    out=false;
end
%check if any elements are greater than 4
if any(m>4)
    out=false;
end
%check for any repeat values in columns
for j=1:C
        a=m(:,j);
        a=sort(a');
        if  a~=validnumbers
            out=false;
        end
end

%check for any repeat values in rows
for i=1:R
        b=m(i,:);
        sort(b);
        if  b~=validnumbers
            out=false;
        end
end
%check if any number is repeated within the individual squares
        submatrix1=m([1 2],[1 2]);
        if sort(reshape(submatrix1,1,[]))~=[1 2 3 4]
            out=false;
        end

         submatrix2=m([3 4],[1 2]);
          if sort(reshape(submatrix2,1,[]))~=[1 2 3 4]
              out=false;
          end

         submatrix3=m([1 2],[3 4]);
          if sort(reshape(submatrix3,1,[]))~=[1 2 3 4]
              out=false;
          end

          submatrix4=m([3 4],[3 4]);
          if sort(reshape(submatrix4,1,[]))~=[1 2 3 4]
              out=false;
          end