Inplace array reversal

README.md

@@ -127,6 +127,7 @@ A collection of JavaScript problems and solutions for studying algorithms.
 - [H-Index](src/array/h-index.js)
 - [H-Index II](src/array/h-index-ii.js)
 - [Pour Water](src/array/pour_water.js)
+- [Inplace Array Reversal](src/array/inplace-reverse-array.js)
 
 ### Matrix
 

src/array/inplace-reverse-array.js

@@ -0,0 +1,50 @@
+/**
+ * Reverse Inplace Array
+ *
+ * Given an Array arr.
+ *
+ * We want to reverse order of elements inside .
+ * We will also take edge cases into account 
+ * For eg:- In case parameter passed is null or undefined we may want to throw error
+ *          In case parameter passed is not an array
+ *          In case parameter passed has length 0
+ *
+ * For example, given
+ *
+ * arr = [1,2,3,4,5,6,7,8,9]
+ * We should return
+ * [9,8,7,6,5,4,3,2,1]
+ * 
+ */
+
+/**
+ * @param {number[]} arr
+ * @return {number[]} arr
+ */
+function inPlaceArrayReverse(arr) {
+  // edge cases
+  if(!arr){
+    throw new Error('undefined input');
+  }
+
+  if(!Array.isArray(arr)){
+    throw new Error('not an array')
+  }
+
+  if(arr.length === 0){
+    throw new Error('array empty')
+  } 
+
+  var len = arr.length - 1;
+  for(let j=0; j<len/2; j++ ){
+    let temp = arr[j];
+    arr[j] = arr[len-j];
+    arr[len-j] = temp;
+  }  
+
+  return arr;
+}
+
+let testArray = [1,2,3,4,5,6];
+
+console.log('Printing the inplace reverse of a given array: ', inPlaceArrayReverse(testArray));