From 6191da80471187e447f7d40bd9f10258905cb25b Mon Sep 17 00:00:00 2001
From: David Phillips <david@sighup.nz>
Date: Wed, 5 Apr 2017 23:12:38 +1200
Subject: Add histogram sort

---
 hist-sort.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 hist-sort.c

(limited to 'hist-sort.c')

diff --git a/hist-sort.c b/hist-sort.c
new file mode 100644
index 0000000..409dcb1
--- /dev/null
+++ b/hist-sort.c
@@ -0,0 +1,76 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define RANGE 10000
+#define COUNT 10000
+
+int is_sorted(unsigned int *data, size_t length)
+{
+	size_t i = 0;
+
+	for (i = 0; i < length-1; i++)
+		if (data[i] > data[i+1])
+			return 0;
+
+	return 1;
+}
+
+void fill_random(unsigned int *data, size_t length, unsigned int max)
+{
+	size_t i = 0;
+
+	for (i = 0; i < length; i++)
+		data[i] = rand()%max+1;
+}
+
+void sort(unsigned int *data, size_t length, unsigned int max)
+{
+	size_t *hist = calloc(max+1, sizeof(size_t));
+	size_t i = 0;
+	size_t j = 0;
+
+	for (i = 0; i < length; i++) {
+		hist[data[i]]++;
+	}
+
+	j = 0;
+	for (i = 0; i < max+1; i++) {
+		for (; hist[i]; hist[i]--, j++)
+			data[j] = i;
+	}
+}
+
+void dump_data(unsigned int *data, size_t length)
+{
+	size_t i = 0;
+
+	for (i = 0; i < length; i++)
+		printf("%d, ", data[i]);
+
+	fputc('\n', stdout);
+}
+
+int main(int argc, char **argv)
+{
+	unsigned int *data = calloc(COUNT, sizeof(unsigned int));
+
+	if (!data) {
+		perror("calloc");
+		return 1;
+	}
+
+	srand(time(NULL));
+
+	fill_random(data, COUNT, RANGE);
+
+	//dump_data(data, COUNT);
+	sort(data, COUNT, RANGE);
+	//dump_data(data, COUNT);
+
+	if (!is_sorted(data, COUNT)) {
+		fprintf(stderr, "Failed: out of order\n");
+	} else {
+		printf("Success.\n");
+	}
+}
-- 
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