2d array swap

[silversnake]

hi all, I'm trying to swap two array location within a 2d array using the swap function. I know that how to swap with in a 1d array eg " swap(array, inner, inner+1); " but how do I use swap within a 2da array?

e.g

1 2 3
4 5 6

I want to swap the columns only.

1 2 6
4 5 3

can someone please help me with this problem
thanks

[sicarie]

What have you tried on this? (where are you getting stuck?)

[AdrianH]

I am not familiar with the swap that you are referring to. I do not see it in the standard algorithms.

One can do swapping arrays using recursion. I.e. write a function that takes in two 2d arrays, then in a loop swap each element individually.

pseudo code:

template <int SIZE>
function swap2d (int & array1[SIZE], int & array2[SIZE])
  for i = 0 to SIZE-1
    swap1d(array1[i], array2[i])
  end for
end function
 
template <int SIZE>
function swap1d (int & array1[SIZE], int & array2[SIZE])
  for i = 0 to SIZE-1
    swap(array1[i], array2[i])
  end for
end function
 

Note, if you are doing fairly large array swapping, you may want to reconsider using the older style of arrays that are an array of pointers to an array of elements, and then just swap the pointers. It is far more efficient.


Adrian

[Ganon11]

I think the OP is talking about a swap function to swap two integer values within an array:

int *myArray = {1, 2, 3, 4, 5, 6};
swap(myArray, 0, 3);
// myArray is now {4, 2, 3, 1, 5, 6};

[silversnake]

What have you tried on this? (where are you getting stuck?)

 if (dir == 'v') // v is the command for column move
    {
      for (v=0; v<COLS-1; v--)  // step through the array
 
      {
 
       temp = puzzle[v][rowcol];
 
 
       puzzle[v][rowcol] = puzzle[v][rowcol-1];
       puzzle[v][rowcol-1] = temp;
 
     }
 
     printPuzzle(puzzle); // print result
  }
 
}

[Savage]

One question:

why is v-- in for loop?


I fear that this loop will never end.

If u have need of v-- than v is aint gona start from zero it will start from COL-1 and loop will execute while v>=0.

Savage

[silversnake]

it works now thanks for the help.

[AdrianH]

I think the OP is talking about a swap function to swap two integer values within an array:

int *myArray = {1, 2, 3, 4, 5, 6};
swap(myArray, 0, 3);
// myArray is now {4, 2, 3, 1, 5, 6};

I couldn't find any reference to swap with that signature.


Adrian

[sicarie]

I couldn't find any reference to swap with that signature.


Adrian

I think it's a user-defined function. I was only able to find one that was applicable to strings, not ints.