Two Dimensional Arrays
The data type array2 can be used to store a number of objects of
an arbitrary type T. The objects can be accessed uniquely by two indices
from two integer intervals I and J.
This data type is closely related to One Dimensional
Arrays.
Example
The following program shows how to use Two Dimensional Arrays. It generates
an array A of 10 times 20 ints with indices from 1 to 10 and
31 to 50. Then it assigns value i+j to A(i,j).
Finally, it shows how elements can be accessed by their indices.
#include <LEDA/core/array2.h>
int main()
{
leda::array2<int> A(1,20,31,50);
int i;
for (i=1; i<=10; i++) {
int j;
for (j=31;j<=50; j++) {
A(i,j)=i+j;
}
}
std::cout << A(3,43) << " " << A(10,31) << std::endl;
return 0;
}
Strengths
- access and insertion of objects by indices in constant time
- induced order on objects
- index sets can be arbitrary intervals of integers (do not have to
start at 0)
- array bounds are checked
Disadvantages
- waste of space if array is bigger than the currentl number of objects
(alternatives: Linear Lists, Sets)
- searching for an element is slow (proportional to the size of the
array) (alternative: Sets)
- no simple iteration over the current elements (alternatives: Linear
Lists, Sets)
- initialization is necessary
Tips
- Use Two Dimensional Arrays if you know the number of elements to store
(at least approximately) beforehand and you need to access the elements
efficiently by two integer indices.
- Otherwise consider using one of the combinations list of lists, set
of sets, list of sets, set of lists, of Linear
Lists or Sets.
- For matrix operations consider using Double
Valued Matrices, Matrices
with Integer Entries.
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See also:
One Dimensional Arrays
Linear Lists
Sets
Double Valued Matrices
Matrices with Integer Entries
Two-Dimensional Node Array
Manual Entries:
Manual
Page Two Dimensional Arrays
User
Defined Parameter Types
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