Computer_Science/leetcode/59-spiral_matrix_II.c


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/**
 * Return an array of arrays.
 * Note: The returned array must be malloced, assume caller calls free().
 */
int** generateMatrix(int n) {
	int **matrix = malloc(sizeof(int *) * n);
	int offset = 0;
	int maxOffset = n / 2 + 1;
	int index = 1;
	int i;

	for(i = 0; i < n; i++)
		*(matrix + i) = malloc(sizeof(int) * n);

	for(offset = 0; offset < maxOffset; offset++, n -= 2) {
		if(n == 0)
			break;
		else if(n == 1) {
			matrix[offset][offset] = index++;
			break;
		} else {
			for(i = 0; i < n; i++)
				matrix[offset][offset + i] = index++;
			for(i = 1; i < n; i++)
				matrix[offset + i][offset + n - 1] = index++;
			for(i = 1; i < n; i++)
				matrix[offset + n - 1][offset + n - 1 - i] = index++;
			for(i = 1; i < n - 1; i++)
				matrix[offset + n - 1 - i][offset] = index++;
		}
	}

	return matrix;
}