shufflechars: Shuffle characters around.

1 files changed, 59 insertions, 0 deletions

diff --git a/shufflechars.c b/shufflechars.c
new file mode 100644
index 0000000..84a2c55
--- /dev/null
+++ b/shufflechars.c
@@ -0,0 +1,59 @@
+/*
+ * Copyright (C) 2015  Tomasz Kramkowski <tk@the-tk.com>
+ *
+ * This program is free software. It is licensed under version 3 of the
+ * GNU General Public License.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see [http://www.gnu.org/licenses/].
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <string.h>
+#include <time.h>
+
+static inline unsigned rand_to_max(unsigned max)
+{
+	double random;
+
+	while ((random = rand()) == (double)RAND_MAX);
+
+	return random / (double)RAND_MAX * (double)max;
+}
+
+int main(int argc, char **argv)
+{
+	size_t length;
+	char *text, *dest;
+
+	srand(time(NULL));
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s <text>\a\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	text = argv[1];
+	length = strlen(text);
+
+	bool relocated[length];
+
+	memset(relocated, 0, length);
+	dest = malloc(length + 1);
+
+	for (size_t i = 0; i < length; i++) {
+		size_t index;
+		while (index = rand_to_max(length), relocated[index])
+			;
+
+		dest[i] = text[index];
+		relocated[index] = true;
+	}
+
+	dest[length] = '\0';
+
+	printf("%s\n", dest);
+
+	return EXIT_SUCCESS;
+}