From e9e3ea4684332263fa7afbdd0e18780158888e7d Mon Sep 17 00:00:00 2001
From: Vedas Dixit <111585043+vedas-dixit@users.noreply.github.com>
Date: Wed, 15 Nov 2023 19:22:57 +0530
Subject: [PATCH] Implemented Partition Problem, Recursive problem (#1582)
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* Add Tug of War solution using backtracking

* Updated Documentation in README.md

* Added Tug of war problem link

* Updated Documentation in README.md

* Updated Documentation in README.md

* Refactor tugOfWar: remove unused vars, optimize initialization, and remove redundant checks

* Added Function Export Statment

* Updated Documentation in README.md

* Resolved Code Style --Prettier

* Rename "backtrack" to "recurse"

* Fix test case: The difference needs to be exactly 1.

* Code Modification: subsets should have sizes as close to n/2 as possible

* Updated test-case of TugOfWar

* Changed TugOfWar problem to Partition

* Modified partition problem

* Updated Documentation in README.md

* fixed code style

---------

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Lars Müller <34514239+appgurueu@users.noreply.github.com>
---
 DIRECTORY.md                     |  2 ++
 Recursive/Partition.js           | 39 ++++++++++++++++++++++++++++++++
 Recursive/test/Partition.test.js | 24 ++++++++++++++++++++
 3 files changed, 65 insertions(+)
 create mode 100644 Recursive/Partition.js
 create mode 100644 Recursive/test/Partition.test.js

diff --git a/DIRECTORY.md b/DIRECTORY.md
index 1b2c40b3c..2ede55266 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -160,6 +160,7 @@
   * [NumberOfIslands](Graphs/NumberOfIslands.js)
   * [PrimMST](Graphs/PrimMST.js)
 * **Hashes**
+  * [MD5](Hashes/MD5.js)
   * [SHA1](Hashes/SHA1.js)
   * [SHA256](Hashes/SHA256.js)
 * **Maths**
@@ -300,6 +301,7 @@
   * [KochSnowflake](Recursive/KochSnowflake.js)
   * [LetterCombination](Recursive/LetterCombination.js)
   * [Palindrome](Recursive/Palindrome.js)
+  * [Partition](Recursive/Partition.js)
   * [SubsequenceRecursive](Recursive/SubsequenceRecursive.js)
   * [TowerOfHanoi](Recursive/TowerOfHanoi.js)
 * **Search**
diff --git a/Recursive/Partition.js b/Recursive/Partition.js
new file mode 100644
index 000000000..51465f8e9
--- /dev/null
+++ b/Recursive/Partition.js
@@ -0,0 +1,39 @@
+/**
+ * @function canPartition
+ * @description Check whether it is possible to partition the given array into two equal sum subsets using recursion.
+ * @param {number[]} nums - The input array of numbers.
+ * @param {number} index - The current index in the array being considered.
+ * @param {number} target - The target sum for each subset.
+ * @return {boolean}.
+ * @see [Partition Problem](https://en.wikipedia.org/wiki/Partition_problem)
+ */
+
+const canPartition = (nums, index = 0, target = 0) => {
+  if (!Array.isArray(nums)) {
+    throw new TypeError('Invalid Input')
+  }
+
+  const sum = nums.reduce((acc, num) => acc + num, 0)
+
+  if (sum % 2 !== 0) {
+    return false
+  }
+
+  if (target === sum / 2) {
+    return true
+  }
+
+  if (index >= nums.length || target > sum / 2) {
+    return false
+  }
+
+  // Include the current number in the first subset and check if a solution is possible.
+  const withCurrent = canPartition(nums, index + 1, target + nums[index])
+
+  // Exclude the current number from the first subset and check if a solution is possible.
+  const withoutCurrent = canPartition(nums, index + 1, target)
+
+  return withCurrent || withoutCurrent
+}
+
+export { canPartition }
diff --git a/Recursive/test/Partition.test.js b/Recursive/test/Partition.test.js
new file mode 100644
index 000000000..929519999
--- /dev/null
+++ b/Recursive/test/Partition.test.js
@@ -0,0 +1,24 @@
+import { canPartition } from '../Partition'
+
+describe('Partition (Recursive)', () => {
+  it('expects to return true for an array that can be partitioned', () => {
+    const result = canPartition([1, 5, 11, 5])
+    expect(result).toBe(true)
+  })
+
+  it('expects to return false for an array that cannot be partitioned', () => {
+    const result = canPartition([1, 2, 3, 5])
+    expect(result).toBe(false)
+  })
+
+  it('expects to return true for an empty array (0 elements)', () => {
+    const result = canPartition([])
+    expect(result).toBe(true)
+  })
+
+  it('Throw Error for Invalid Input', () => {
+    expect(() => canPartition(123)).toThrow('Invalid Input')
+    expect(() => canPartition(null)).toThrow('Invalid Input')
+    expect(() => canPartition(undefined)).toThrow('Invalid Input')
+  })
+})