- A two-dimensional static (= not dynamic)
array
is defined using the following syntax in C++:
TYPE arrayName [ size1 ] [ size2 ];The sizes must be a constant value.
- Example:
int a[3][3]; // a 3x3 "matrix" double b[4][5]; // 4 rows, 5 columns
- The syntax to access
an element in a multi-dimensional array
in C++ is the same as in
Java:
arrayName [ index1 ] [ index2 ]
- Example: print a matrix
int a[3][3]; int i, j; for (i = 0; i < 3; i++) for (j = 0; j < 3; j++) cout << a[i][j];
- C++ does not support
multi-dimensional dynamic arrays
- However, you can
organize a
one-dimensional array into
a multi-dimensional array
yourself !!!
In other words, if you want dynamic multi-dimensional arrays, you have to do it yourself
- Storing a two-dimensional array
linearly
as a
one-dimensional array
(i.e., on one row):
Storage scheme:
- Store all element in row 0 first
- Then store all element in row 0 next
- And so on
- Compute the index for the element a[i][j]
- From the example above, we can see that the
element a[i][j] is
stored at the
i*N + j element in the
linearized (one-row) array
(N is the number of columns)
- From the example above, we can see that the
element a[i][j] is
stored at the
i*N + j element in the
linearized (one-row) array
- Here is the code to store a
nRows x nCols array:
int *a; int nRow, nCol; int i, j; nRow = 3; nCol = 4; a = new int[nRows * nCols]; // Make a one-dim array for ( i = 0; i < nRows; i++ ) for ( j = 0; j < nCols; j++ ) { a[ i*nCols + j ] = 1000*i + j; // Store "a[i][j]" as a[i*nCols + j] }
- Example Program:
(Demo above code)
- Prog file: click here