Linear indexing in symmetric matrices

Question

We can access matrices using linear indexing, which follows this pattern

0 1 2

3 4 5

6 7 8

It\'s easy to get the i,j coordinates for this cas

Answer 1

For 0-index based:

int j = 0;
int x = (n-1);
while (idx > x) {
    j++;
    idx=idx-x;
    x--;
}
i=idx;