#!/usr/bin/env cscript

/* SPDX-License-Identifier: GPL-2.0
 *
 * Copyright (C) 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 */

#define _GNU_SOURCE

#include <stdint.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdio.h>
#include <inttypes.h>
#include <errno.h>

enum { PASCALS_TRIANGLE_MAX_ROWS_FOR_UINT64 = 68 };

static uint64_t **create_pascals_triangle(size_t num_rows)
{
	uint64_t **triangle;
	size_t i, j;

	if (!num_rows || num_rows > PASCALS_TRIANGLE_MAX_ROWS_FOR_UINT64) {
		errno = EINVAL;
		return NULL;
	}
	
	triangle = reallocarray(NULL, num_rows + 1, sizeof(*triangle));
	if (!triangle)
		return NULL;
	triangle[num_rows] = NULL;

	for (i = 0; i < num_rows; ++i) {
		triangle[i] = reallocarray(NULL, i + 1, sizeof(**triangle));
		if (!triangle[i]) {
			for (j = 0; j < i; ++j)
				free(triangle[j]);
			free(triangle);
			return NULL;
		}
		triangle[i][0] = triangle[i][i] = 1;
		for (j = 1; j < i; ++j)
			triangle[i][j] = triangle[i - 1][j - 1] + triangle[i - 1][j];
	}

	return triangle;
}

static void free_pascals_triangle(uint64_t **triangle)
{
	size_t i;

	if (!triangle)
		return;

	for (i = 0; triangle[i]; ++i)
		free(triangle[i]);
	free(triangle);
}

static void print_pascals_triangle(FILE *file, uint64_t **triangle)
{
	size_t i, j;

	for (i = 0; triangle[i]; ++i) {
		for (j = 0; j < i + 1; ++j)
			fprintf(file, "%" PRIu64 " ", triangle[i][j]);
		fputc('\n', file);
	}
}

int main(int argc, char *argv[])
{
	uint64_t **triangle;
	size_t num_rows;
	char *endptr;

	if (argc != 2) {
		fprintf(stderr, "Usage: %s ROWS\n", argv[0]);
		return 1;
	}
	
	num_rows = strtoul(argv[1], &endptr, 10);
	if (!*argv[1] || *endptr) {
		fprintf(stderr, "ERROR: `%s' is not a valid number\n", argv[1]);
		return 1;
	}

	triangle = create_pascals_triangle(num_rows);
	if (!triangle) {
		perror("ERROR: unable to create triangle");
		return 1;
	}
	print_pascals_triangle(stdout, triangle);
	free_pascals_triangle(triangle);
	
	return 0;
}