From 3a8e33626277146353d3ab60747e2af22fd3d25a Mon Sep 17 00:00:00 2001
From: Abhijeet Tiwari <abhijeet1862@gmail.com>
Date: Wed, 6 Oct 2021 14:45:07 +0530
Subject: [PATCH] added documentation, js standard style and jest testing to
 kadane algorithm file.

---
 Dynamic-Programming/KadaneAlgo.js            | 27 +++++++++++++++-----
 Dynamic-Programming/tests/KadaneAlgo.test.js |  8 ++++++
 2 files changed, 29 insertions(+), 6 deletions(-)
 create mode 100644 Dynamic-Programming/tests/KadaneAlgo.test.js

diff --git a/Dynamic-Programming/KadaneAlgo.js b/Dynamic-Programming/KadaneAlgo.js
index 1e275dd09..5d60103f9 100644
--- a/Dynamic-Programming/KadaneAlgo.js
+++ b/Dynamic-Programming/KadaneAlgo.js
@@ -1,20 +1,35 @@
-function KadaneAlgo (array) {
+/* Kadane's algorithm is one of the most efficient ways to
+ * calculate the maximum contiguos subarray sum for a given array.
+ * Below is the implementation of kadanes's algorithm along with
+ * some sample test cases.
+ * There might be a special case in this problem if al the elements
+ * of the given array are negative. In such a case, the maximum negative
+ * value present in the array is the answer.
+ *
+ * Reference article :- https://www.geeksforgeeks.org/largest-sum-contiguous-subarray/
+ */
+
+function kadaneAlgo (array) {
   let cummulativeSum = 0
-  let maxSum = 0
+  let maxSum = Number.NEGATIVE_INFINITY // maxSum has the least posible value
   for (let i = 0; i < array.length; i++) {
     cummulativeSum = cummulativeSum + array[i]
-    if (cummulativeSum < 0) {
-      cummulativeSum = 0
-    } else if (maxSum < cummulativeSum) {
+    if (maxSum < cummulativeSum) {
       maxSum = cummulativeSum
+    } else if (cummulativeSum < 0) {
+      cummulativeSum = 0
     }
   }
   return maxSum
   // This function returns largest sum contiguous sum in a array
 }
 function main () {
+  // input array
   const myArray = [1, 2, 3, 4, -6]
-  const result = KadaneAlgo(myArray)
+  // calling the function
+  const result = kadaneAlgo(myArray)
+  // result is the variable for storing the ourput of kadaneAlgo function
   console.log(result)
 }
 main()
+module.exports = { kadaneAlgo }
diff --git a/Dynamic-Programming/tests/KadaneAlgo.test.js b/Dynamic-Programming/tests/KadaneAlgo.test.js
new file mode 100644
index 000000000..e0b7e6fd4
--- /dev/null
+++ b/Dynamic-Programming/tests/KadaneAlgo.test.js
@@ -0,0 +1,8 @@
+const fc = require('../kadaneAlgo')
+test('test1', () => {
+  expect(fc.kadaneAlgo([1, 2, 3, 4, 5])).toBe(15)
+})
+
+test('test2', () => {
+  expect(fc.kadaneAlgo([-1, -2, -3, -4, 5])).toBe(5)
+})