How to insert a value in double pointer (2D array) in a specific location

Question

int **p = NULL;

p = (int **) malloc(sizeof (int *) * 3);
for (int i = 0; i < 3; i++)
    p[i] = (int *) malloc(sizeof (int) * 4);

In this code a double pointer is used as 2D array. My questions are

How can i do this?

If you use the allocated space as a 2D array, does that not imply that you will access elements via the indexing operator (`[]`)? In pairs, since it's 2D? — John Bollinger, Feb 04 '19 at 18:18
@EugeneSh i mean if i allocated double pointer then how can i put values in it and insert a value at a specific location — SUPREMESOUL, Feb 04 '19 at 18:24
I should probably mention that [you shouldn't cast the result of `malloc()`](https://stackoverflow.com/a/605858/8420233). — absoluteAquarian, Feb 04 '19 at 21:20
Or, with `*(*(p + x) + y)` which is the same as `*(p[x] + y)` which is the same as `p[x][y]`... — David C. Rankin, Feb 04 '19 at 21:36

score 2 · Accepted Answer · answered Feb 04 '19 at 18:27

2

Just using index operator as 2D array.

if you want to insert 1 at every position.

for (int i = 0; i < 3; i++)
{
    for (int j = 0; j < 4; j++)
        p[i][j] = 1;
}

if you want to insert value 2 at specific location at row i, column j

p[i][j] = 2;

answered Feb 04 '19 at 18:27

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1 Answers1