From 440ba3af85349324c86f92715338924c54c019b9 Mon Sep 17 00:00:00 2001
From: Philippe-Cholet <44676486+Philippe-Cholet@users.noreply.github.com>
Date: Fri, 29 Mar 2024 09:40:05 +0100
Subject: [PATCH 1/2] k_smallest(0) and variants: consume the iterator

The iterator can have side effects so I think it should be consumed in all cases, even k=0.
If there are no side-effect then maybe the compiler will optimize it away.
---
 src/k_smallest.rs | 1 +
 src/lib.rs        | 1 +
 2 files changed, 2 insertions(+)

diff --git a/src/k_smallest.rs b/src/k_smallest.rs
index b909887f5..97f0ee02a 100644
--- a/src/k_smallest.rs
+++ b/src/k_smallest.rs
@@ -42,6 +42,7 @@ where
     }
 
     if k == 0 {
+        iter.last();
         return Vec::new();
     }
     let mut iter = iter.fuse();
diff --git a/src/lib.rs b/src/lib.rs
index a297a6d80..65909fcdd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2972,6 +2972,7 @@ pub trait Itertools: Iterator {
         use alloc::collections::BinaryHeap;
 
         if k == 0 {
+            self.last();
             return Vec::new().into_iter();
         }
 

From 80c2b304518aaff534922a923d7eb04ef986a78d Mon Sep 17 00:00:00 2001
From: Philippe-Cholet <44676486+Philippe-Cholet@users.noreply.github.com>
Date: Fri, 29 Mar 2024 09:44:28 +0100
Subject: [PATCH 2/2] k_smallest(1) and variants: use `min[_by]`

Like with `tail(1)`, I think we should leverage a possible faster specialization.
---
 src/k_smallest.rs | 3 +++
 src/lib.rs        | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/src/k_smallest.rs b/src/k_smallest.rs
index 97f0ee02a..7b2f62ea1 100644
--- a/src/k_smallest.rs
+++ b/src/k_smallest.rs
@@ -45,6 +45,9 @@ where
         iter.last();
         return Vec::new();
     }
+    if k == 1 {
+        return iter.min_by(comparator).into_iter().collect();
+    }
     let mut iter = iter.fuse();
     let mut storage: Vec<I::Item> = iter.by_ref().take(k).collect();
 
diff --git a/src/lib.rs b/src/lib.rs
index 65909fcdd..ff14cf94e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2975,6 +2975,9 @@ pub trait Itertools: Iterator {
             self.last();
             return Vec::new().into_iter();
         }
+        if k == 1 {
+            return self.min().into_iter().collect_vec().into_iter();
+        }
 
         let mut iter = self.fuse();
         let mut heap: BinaryHeap<_> = iter.by_ref().take(k).collect();