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Merging Two-Dimensional Arrays (Matrices)

In the article Merging One Dimensional Arrays, we discussed how to merge one-dimensional arrays, in this article we will be discussing about the merging of two-dimensional arrays. Merging as you know is the process of combining two similar things. In the context of arrays, it means to form a big array from two smaller arrays which has all the elements from both the arrays.

In case of one-dimensional arrays there is only one way in which two arrays can be merged but in case of two-dimensional arrays there are two ways.

Suppose, we have the following two 2d arrays (matrices):

mat1={
      {1, 2, 3},
      {4, 5, 6},
      {7, 8, 9}
     }

and

mat2={
      {10, 11, 12},
      {13, 14, 15},
      {16, 17, 18}
     }
then they can be merged in the following two ways:
merge_row={
           {1, 2, 3, 10, 11, 12},
           {4, 5, 6, 13, 14, 15},
           {7, 8, 9, 16, 17, 18}
          }
merge_col={
           {1,  2,  3},
           {4,  5,  6},
           {7,  8,  9},
           {10, 11, 12},
           {13, 14, 15},
           {16, 17, 18}
          }

Now that you know the funda, we move on to the example program to illustrate this:

  // example program to illustrate
  // merging of two-dimensional or
  // 2d arrays(matrices)  
  #include<iostream.h>

  #define ROW1 3
  #define ROW2 3
  #define COL1 3
  #define COL2 3

  void main(void)
  {
   int i,j;
   int matrix1[ROW1][COL1];
   int matrix2[ROW2][COL2];

   // these will store merged
   // matrices
   int merge_row[ROW1][COL1+COL2];
   int merge_col[ROW1+ROW2][COL1];

   // input the elements
   cout<<"Input elements for MATRIX 1:\n";
   for(i=0;i<ROW1;i++)
   {
    cout<<"ROW "<<i+1<<":\n";
    for(j=0;j<COL1;j++)
    cin>>matrix1[i][j];
   }

   cout<<"\nInput elements for MATRIX 2:\n";
   for(i=0;i<ROW2;i++)
   {
    cout<<"ROW "<<i+1<<":";
    for(j=0;j<COL2;j++)
    cin>>matrix2[i][j];
   }
   //input complete

   // merge matrices
   // row merge starts
   for(i=0;i<ROW1;i++)
     for(j=0;j<COL1;j++)
       merge_row[i][j]=matrix1[i][j];

   for(i=0;i<ROW2;i++)
     for(j=0;j<COL2;j++)
       merge_row[i][j+COL2]=matrix2[i][j];
   // row merge complete

   // column merge starts
   for(i=0;i<ROW1;i++)
     for(j=0;j<COL1;j++)
       merge_col[i][j]=matrix1[i][j];

   for(i=0;i<ROW2;i++)
     for(j=0;j<COL2;j++)
       merge_col[i+ROW1][j]=matrix2[i][j];
   // column merge complete

   // show the merged martices
   cout<<"\nROW Merge:\n\n";
   for(i=0;i<ROW1;i++)
   {
    for(j=0;j<COL1+COL2;j++)
      cout<<" "<<merge_row[i][j];
   
    cout<<endl;
   }

   cout<<"\nCOLUMN Merge:\n\n";
   for(i=0;i<ROW1+ROW2;i++)
   {
    for(j=0;j<COL1;j++)
      cout<<" "<<merge_col[i][j];
   
    cout<<endl;
   }
  }

Good-Bye!

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