From 1059dfecb3152b6d33187dfd558d16de64c5cc9c Mon Sep 17 00:00:00 2001
From: jacekpoz <jacekpoz@proton.me>
Date: Mon, 6 May 2024 23:11:16 +0200
Subject: [PATCH] introduce k as the amount of elements in a chunk

---
 libselect/src/normal_select.rs | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/libselect/src/normal_select.rs b/libselect/src/normal_select.rs
index 3378844..11fbfd4 100644
--- a/libselect/src/normal_select.rs
+++ b/libselect/src/normal_select.rs
@@ -42,7 +42,7 @@ impl NormalSelect {
         j
     }
 
-    fn _select(&mut self, list: &mut Vec<u64>, lo: usize, hi: usize, k: usize) -> (usize, u64) {
+    fn _select(&mut self, list: &mut Vec<u64>, lo: usize, hi: usize, ord_stat: usize, k: usize) -> (usize, u64) {
         if lo == hi {
             return (lo, list[lo]);
         }
@@ -50,7 +50,7 @@ impl NormalSelect {
         if self.should_print { println!("list: {:?}; lo: {lo}; hi: {hi}", list); }
 
         let mut medians: Vec<u64> = vec![];
-        let mut chunks = list.chunks(5)
+        let mut chunks = list.chunks(k)
             .collect::<Vec<_>>();
 
         for mut chunk in chunks.iter_mut().map(|c| c.to_vec()) {
@@ -66,20 +66,24 @@ impl NormalSelect {
 
         let n = hi - lo;
 
-        let (pivot, _) = self._select(&mut medians, 0, n.div_ceil(5) - 1, (n.div_ceil(5) - 1).div_ceil(2));
+        let (pivot, _) = self._select(&mut medians, 0, n.div_ceil(k) - 1, (n.div_ceil(k) - 1).div_ceil(2), k);
         if self.should_print { println!("pivot: {pivot}"); }
         let r = self.partition(list, lo, hi, pivot);
         if self.should_print { println!("r: {r}"); }
         let i = r - lo + 1;
 
-        if i == k {
+        if i == ord_stat {
             return (r, list[r]);
-        } else if i < k {
-            return self._select(list, r + 1, hi, k - i);
+        } else if i < ord_stat {
+            return self._select(list, r + 1, hi, ord_stat - i, k);
         } else {
-            return self._select(list, lo, r - 1, k);
+            return self._select(list, lo, r - 1, ord_stat, k);
         }
     }
+
+    pub fn select_k(&mut self, list: &mut Vec<u64>, order_statistic: usize, k: usize) -> u64 {
+        self._select(list, 0, list.len() - 1, order_statistic, k).1
+    }
 }
 
 impl Select for NormalSelect {
@@ -93,7 +97,7 @@ impl Select for NormalSelect {
     }
 
     fn select_mut(&mut self, list: &mut Vec<u64>, order_statistic: usize) -> u64 {
-        self._select(list, 0, list.len() - 1, order_statistic).1
+        self.select_k(list, order_statistic, 5)
     }
 
     fn num_comp(&self) -> u64 {