From 524571e6fb6dd2a7b1339fa5a7a519e19d8216f7 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <inan@aicodix.de>
Date: Thu, 7 Mar 2024 19:45:47 +0100
Subject: [PATCH] added insertion sort and regression test

---
 sort.hh                       | 34 ++++++++++++++++++++++++++++++
 tests/sort_regression_test.cc | 39 +++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 sort.hh
 create mode 100644 tests/sort_regression_test.cc

diff --git a/sort.hh b/sort.hh
new file mode 100644
index 0000000..b1ea7f2
--- /dev/null
+++ b/sort.hh
@@ -0,0 +1,34 @@
+/*
+Some stable sorting algorithms
+
+Copyright 2024 Ahmet Inan <inan@aicodix.de>
+*/
+
+#pragma once
+
+template <typename TYPE>
+static void insertion_sort(TYPE *a, int n)
+{
+	for (int i = 1, j; i < n; ++i) {
+		TYPE t = a[i];
+		for (j = i; j > 0 && a[j-1] > t; --j)
+			a[j] = a[j-1];
+		a[j] = t;
+	}
+}
+
+template <typename TYPE>
+static void insertion_sort(int *p, TYPE *a, int n)
+{
+	p[0] = 0;
+	for (int i = 1, j; i < n; ++i) {
+		TYPE t = a[i];
+		for (j = i; j > 0 && a[j-1] > t; --j) {
+			a[j] = a[j-1];
+			p[j] = p[j-1];
+		}
+		a[j] = t;
+		p[j] = i;
+	}
+}
+
diff --git a/tests/sort_regression_test.cc b/tests/sort_regression_test.cc
new file mode 100644
index 0000000..449c859
--- /dev/null
+++ b/tests/sort_regression_test.cc
@@ -0,0 +1,39 @@
+/*
+Regression Test for sorting
+
+Copyright 2024 Ahmet Inan <inan@aicodix.de>
+*/
+
+#include <random>
+#include <cassert>
+#include <iostream>
+#include <algorithm>
+#include <functional>
+#include "sort.hh"
+
+int main()
+{
+	std::random_device rd;
+	typedef std::default_random_engine generator;
+	typedef std::uniform_int_distribution<int> distribution;
+	auto rand = std::bind(distribution(1, 32), generator(rd()));
+	int a[32], b[32], c[32], d[32], e[32], f[32];
+	for (int loop = 0; loop < 1000000; ++loop) {
+		int size = rand();
+		for (int i = 0; i < size; ++i)
+			a[i] = b[i] = c[i] = d[i] = rand();
+		std::sort(a, a+size);
+		insertion_sort(b, size);
+		for (int i = 0; i < size; ++i)
+			assert(a[i] == b[i]);
+		for (int i = 0; i < size; ++i)
+			e[i] = i;
+		std::stable_sort(e, e+size, [c](int i, int j){ return c[i] < c[j]; });
+		insertion_sort(f, d, size);
+		for (int i = 0; i < size; ++i)
+			assert(e[i] == f[i]);
+	}
+	std::cerr << "Sorting regression test passed!" << std::endl;
+	return 0;
+}
+