hijkl wrote:
> this question was asked by Google..
> "Write a program of spiral matrix"
> ie. it takes inputs and puts in to matrix as a spiral..example.
> given : 3 X 4 matrix
> your input in this order : 1 5 8 9 10 7 4 8 0 2 3 6
> will generate following matrix
>
> 1 5 8 9
> 2 3 6 10
> 0 8 4 7
>
> and big O notation for this..
O(k) where k = mn is the number of inputs and the matrix is m x n.
Let i0 and i1 be top and bottom rows of the unfilled portion; j0 and j1
are left- and rightmost unfilled columns. Then just walk around the
edge of the unfilled space, updating as you go. You're done if there
are no unfilled rows or columns left.
i0 = j0 = 0; i1 = m - 1; j1 = n - 1;
for (;;) {
if (i0 > i1) break;
for (i = i0++, j = j0; j <= j1; j++) a[i][j] = next_input();
if (j0 > j1) break;
for (i = i0, j = j1--; i <= i1; i++) a[i][j] = next_input();
if (i0 > i1) break;
for (i = i1--, j = j1; j >= j0; j--) a[i][j] = next_input();
if (j0 > j1) break;
for (i = i1, j = j0++; i >= i0; i--) a[i][j] = next_input();
}
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