Quick Select Search (#131)

* HeapSort algorithm

* Create QuickSelect.js

* Algorithm to reverse a string.

* Update ReverseString.js

* Update Heapsort.js

* Update QuickSelect.js

Co-authored-by: vinayak <itssvinayak@gmail.com>

maths/ReverseString.js

@@ -0,0 +1,45 @@
+/**
+ * A short example showing how to reverse a string
+ * @flow
+ */
+
+/**
+ * Create a new string and append
+ * @complexity O(n)
+ */
+
+function ReverseStringIterative (string) {
+  let reversedString = ''
+  let index
+
+  for (index = string.length - 1; index >= 0; index--) {
+    reversedString += string[index]
+  }
+
+  return reversedString
+}
+
+/**
+ * JS disallows string mutation so we're actually a bit slower.
+ *
+ * @complexity: O(n)
+ *
+ * 'some' -> 'eoms' -> 'emos'
+ */
+
+function ReverseStringIterativeInplace (string) {
+  const _string = string.split('')
+
+  for (let i = 0; i < Math.floor(_string.length / 2); i++) {
+    const first = _string[i]
+    const second = _string[_string.length - 1 - i]
+    _string[i] = second
+    _string[_string.length - 1 - i] = first
+  }
+
+  return _string.join('')
+}
+
+// testing
+console.log(ReverseStringIterative('Javascript'))
+console.log(ReverseStringIterativeInplace('Javascript'))