From e424ba2a4fafff27feb1ebbc1b95d93d4fdeaa9a Mon Sep 17 00:00:00 2001
From: Andrew Chudinovskyh <andron989@gmail.com>
Date: Sat, 31 Oct 2020 17:33:26 +0200
Subject: [PATCH 1/2] Added QuickSelect  Algorithm

---
 DIRECTORY.md                |  1 +
 Search/QuickSelectSearch.js | 55 +++++++++++++++++++++++++++++++++++++
 2 files changed, 56 insertions(+)
 create mode 100644 Search/QuickSelectSearch.js

diff --git a/DIRECTORY.md b/DIRECTORY.md
index 5b8240d8dd..dea092360e 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -178,6 +178,7 @@
   * [InterpolationSearch](https://github.com/TheAlgorithms/Javascript/blob/master/Search/InterpolationSearch.js)
   * [JumpSearch](https://github.com/TheAlgorithms/Javascript/blob/master/Search/JumpSearch.js)
   * [LinearSearch](https://github.com/TheAlgorithms/Javascript/blob/master/Search/LinearSearch.js)
+  * [QuickSelect](https://github.com/TheAlgorithms/Javascript/blob/master/Search/QuickSelectSearch.js)
   * [StringSearch](https://github.com/TheAlgorithms/Javascript/blob/master/Search/StringSearch.js)
 
 ## Sorts
diff --git a/Search/QuickSelectSearch.js b/Search/QuickSelectSearch.js
new file mode 100644
index 0000000000..724fb8d13e
--- /dev/null
+++ b/Search/QuickSelectSearch.js
@@ -0,0 +1,55 @@
+/*
+ * Places the `k` smallest elements in `array` in the first `k` indices: `[0..k-1]`
+ * Modifies the passed in array *in place*
+ * Returns a slice of the wanted elements for convenience
+ * Efficient mainly because it never performs a full sort.
+ *
+ * The only guarantees are that:
+ *
+ * - The `k`th element is in its final sort index (if the array were to be sorted)
+ * - All elements before index `k` are smaller than the `k`th element
+ *
+ * [Reference](http://en.wikipedia.org/wiki/Quickselect)
+ */
+function quickSelectSearch(array, k) {
+  if (!array || array.length <= k) {
+    throw new Error('Invalid arguments');
+  }
+
+  let from = 0;
+  let to = array.length - 1;
+  while (from < to) {
+    let left = from;
+    let right = to;
+    const pivot = array[Math.ceil((left + right) * 0.5)];
+
+    while (left < right) {
+      if (array[left] >= pivot) {
+        const tmp = array[left];
+        array[left] = array[right];
+        array[right] = tmp;
+        --right;
+      } else {
+        ++left;
+      }
+    }
+
+    if (array[left] > pivot) {
+      --left;
+    }
+
+    if (k <= left) {
+      to = left;
+    } else {
+      from = left + 1;
+    }
+  }
+  return array;
+}
+
+/* ---------------------------------- Test ---------------------------------- */
+
+const arr = [1121111, 21, 333, 41, 5, 66, 7777, 28, 19, 11110]
+console.log(quickSelectSearch(arr, 5)); // [ 19, 21, 28, 41, 5, 66, 333, 11110, 1121111, 7777 ]
+console.log(quickSelectSearch(arr, 2)); // [ 19, 5, 21, 41, 28, 333, 11110, 1121111, 7777, 66 ]
+console.log(quickSelectSearch(arr, 7)); // [ 19, 5, 21, 41, 28, 66, 333, 7777, 11110, 1121111 ]

From 83b05cde159e863b0bb278116b69f9df3e1ac6da Mon Sep 17 00:00:00 2001
From: Andrew Chudinovskyh <andron989@gmail.com>
Date: Sat, 31 Oct 2020 17:53:08 +0200
Subject: [PATCH 2/2] style fixes

---
 Search/QuickSelectSearch.js | 38 ++++++++++++++++++-------------------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/Search/QuickSelectSearch.js b/Search/QuickSelectSearch.js
index 724fb8d13e..7a8c57bd3d 100644
--- a/Search/QuickSelectSearch.js
+++ b/Search/QuickSelectSearch.js
@@ -11,45 +11,45 @@
  *
  * [Reference](http://en.wikipedia.org/wiki/Quickselect)
  */
-function quickSelectSearch(array, k) {
+function quickSelectSearch (array, k) {
   if (!array || array.length <= k) {
-    throw new Error('Invalid arguments');
+    throw new Error('Invalid arguments')
   }
 
-  let from = 0;
-  let to = array.length - 1;
+  let from = 0
+  let to = array.length - 1
   while (from < to) {
-    let left = from;
-    let right = to;
-    const pivot = array[Math.ceil((left + right) * 0.5)];
+    let left = from
+    let right = to
+    const pivot = array[Math.ceil((left + right) * 0.5)]
 
     while (left < right) {
       if (array[left] >= pivot) {
-        const tmp = array[left];
-        array[left] = array[right];
-        array[right] = tmp;
-        --right;
+        const tmp = array[left]
+        array[left] = array[right]
+        array[right] = tmp
+        --right
       } else {
-        ++left;
+        ++left
       }
     }
 
     if (array[left] > pivot) {
-      --left;
+      --left
     }
 
     if (k <= left) {
-      to = left;
+      to = left
     } else {
-      from = left + 1;
+      from = left + 1
     }
   }
-  return array;
+  return array
 }
 
 /* ---------------------------------- Test ---------------------------------- */
 
 const arr = [1121111, 21, 333, 41, 5, 66, 7777, 28, 19, 11110]
-console.log(quickSelectSearch(arr, 5)); // [ 19, 21, 28, 41, 5, 66, 333, 11110, 1121111, 7777 ]
-console.log(quickSelectSearch(arr, 2)); // [ 19, 5, 21, 41, 28, 333, 11110, 1121111, 7777, 66 ]
-console.log(quickSelectSearch(arr, 7)); // [ 19, 5, 21, 41, 28, 66, 333, 7777, 11110, 1121111 ]
+console.log(quickSelectSearch(arr, 5)) // [ 19, 21, 28, 41, 5, 66, 333, 11110, 1121111, 7777 ]
+console.log(quickSelectSearch(arr, 2)) // [ 19, 5, 21, 41, 28, 333, 11110, 1121111, 7777, 66 ]
+console.log(quickSelectSearch(arr, 7)) // [ 19, 5, 21, 41, 28, 66, 333, 7777, 11110, 1121111 ]