allocate a memory for a matrix (n*1)

Question

I want to create a matrix of n*1 (a matrix of one column. n can be any integer)

I think It should be something like:

int mat[][1];
cin >> n;
*mat = new int[n]*;

any help appreciated!

A matrix that has only one column is a vector. Why don't you just use `ìnt mat[n]` ? — carlito, May 25 '13 at 00:08
There are many SO questions on this topic, search for dynamic memory allocation or variable length array. — jerry, May 25 '13 at 00:08
but I want it to be a matrix (two pointers). I know how to define a vector, but I want a matrix. — Alon Shmiel, May 25 '13 at 00:12
http://stackoverflow.com/questions/105653/int-matrix-with-pointers-in-c-memory-allocation-confusion?rq=1 — user1520427, May 25 '13 at 00:17

score 3 · Accepted Answer · answered May 25 '13 at 00:25

If you declare your matrix as:

int mat[][1];

It means that you are not doing dynamic memory allocation.

You should do the following:

int **mat = new int*[n]; //n is number of rows
for (int i = 0; i < n ;++i)
{
   mat[i] = new int[1];
}

Anyway, you should prefer to use std::vector instead of using dynamic allocated arrays, especially when you have only 1 column.

kotlomoy · Answer 2 · 2013-05-25T00:31:52.317

1

int * * mat = new int * [ n ];

edited May 25 '13 at 00:31

answered May 25 '13 at 00:08

kotlomoy

thank you but I want a matrix that each row has a pointer to int. – Alon Shmiel May 25 '13 at 00:11

2 Answers2