Initial commit

1 files changed, 99 insertions, 0 deletions

diff --git a/example.c b/example.c
new file mode 100755
index 0000000..9db558a
--- /dev/null
+++ b/example.c
@@ -0,0 +1,99 @@
+#!/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;
+}