Merge branch 'release/1.1.0'

Author: ecgan

README.md

@@ -17,6 +17,7 @@ npm run test
 
 ## Solutions
 
-| # | Title | Difficulty | Topics |
-|--:| ------|------------|--------|
+| LeetCode # | Title | Difficulty | Topics |
+|-----------:|:------|:-----------|:-------|
 | 1 | [Two Sum](/problems/two-sum) | Easy | Array, hash table |
+| 136 | [Single Number](/problems/single-number) | Easy | Hash table, bit manipulation |

package.json

@@ -1,6 +1,6 @@
 {
   "name": "leetcode",
-  "version": "1.0.0",
+  "version": "1.1.0",
   "description": "My solutions for LeetCode problems.",
   "main": "index.js",
   "scripts": {

problems/single-number/README.md

@@ -0,0 +1,29 @@
+# Two Sum
+
+[Link to LeetCode page](https://leetcode.com/problems/two-sum/)
+
+Difficulty: Easy
+
+Topics: Hash table, bit manipulation.
+
+## Solution Explanation
+
+This solution uses the [bitwise XOR](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators#(Bitwise_XOR)) operator to return the unique value in the array.
+
+To illustrate the bitwise XOR operation using the given Example 2 from LeetCode page:
+
+```text
+Input: [4,1,2,1,2]
+
+Bitwise XOR operation with 0 on the elements:
+0 ^ 4 ^ 1 ^ 2 ^ 1 ^ 2
+> 4
+```
+
+We want to go through every element in the array, perform the bitwise XOR operation, and return a single value output. Instead of the conventional `for` loop, we use array's [`reduce()`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce) function to achieve this, which is more succinct.
+
+## Complexity Analysis
+
+Time complexity: O(n) because we go through every elements in the array once.
+
+Space complexity: O(1) because the memory used is always the same regardless of the number of elements.

problems/single-number/solution.js

@@ -0,0 +1,7 @@
+const singleNumber = (nums) => {
+  return nums.reduce((acc, cur) => {
+    return acc ^ cur
+  }, 0)
+}
+
+module.exports = singleNumber

problems/single-number/solution.test.js

@@ -0,0 +1,17 @@
+const singleNumber = require('./solution')
+
+test('Sample 1', () => {
+  const input = [2, 2, 1]
+
+  const result = singleNumber(input)
+
+  expect(result).toBe(1)
+})
+
+test('Sample 2', () => {
+  const input = [4, 1, 2, 1, 2]
+
+  const result = singleNumber(input)
+
+  expect(result).toBe(4)
+})