From 7d6418220e9aa69cf934a3a767ada5452faac931 Mon Sep 17 00:00:00 2001
From: Ahmet Inan <inan@aicodix.de>
Date: Sat, 9 Mar 2024 20:49:52 +0100
Subject: [PATCH] use median of three to increase our chances

---
 quick_select.hh | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/quick_select.hh b/quick_select.hh
index 31ae9b0..d0a3929 100644
--- a/quick_select.hh
+++ b/quick_select.hh
@@ -18,11 +18,21 @@ static inline void swap(TYPE *a, int i, int j)
 	a[j] = t;
 }
 
+template <typename TYPE>
+static inline void sort(TYPE *a, int i, int j, int k)
+{
+	if (a[i] > a[j])
+		swap(a, i, j);
+	if (a[i] > a[k])
+		swap(a, i, k);
+	if (a[j] > a[k])
+		swap(a, j, k);
+}
+
 template <typename TYPE>
 static int partition(TYPE *a, int l, int h)
 {
-	int p = (l + h) / 2;
-	swap(a, p, h);
+	sort(a, (l + h) / 2, h, l);
 	for (int i = l; i < h; ++i)
 		if (a[i] < a[h])
 			swap(a, i, l++);