Update README.md

Author: soapyigu

README.md

@@ -15,6 +15,12 @@
 * [Search](#search)
 * [Sort](#sort)
 
+## Companies
+* [Google](#google)
+* [Facebook](#facebook)
+* [Linkedin](#linkedin)
+* [Microsoft](#microsoft)
+
 ## Array
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
@@ -111,6 +117,7 @@
 [Best Time to Buy and Sell Stock](https://leetcode.com/problems/best-time-to-buy-and-sell-stock/)| [Swift](./DP/BestTimeBuySellStock.swift)| Easy| O(n)| O(1)|
 [Coin Change](https://leetcode.com/problems/coin-change/)| [Swift](./DP/CoinChange.swift)| Medium| O(n^2)| O(n)|
 [Longest Increasing Subsequence](https://leetcode.com/problems/longest-increasing-subsequence/)| [Swift](./DP/LongestIncreasingSubsequence.swift)| Medium| O(n^2)| O(n)|
+[Perfect Squares](https://leetcode.com/problems/perfect-squares/)| [Swift](./DP/PerfectSquares.swift)| Medium| O(n^2)| O(n)|
 [House Robber](https://leetcode.com/problems/house-robber/)| [Swift](./DP/HouseRobber.swift)| Easy| O(n)| O(1)|
 [House Robber II](https://leetcode.com/problems/house-robber-ii/)| [Swift](./DP/HouseRobberII.swift)| Medium| O(n)| O(1)|
 [Maximum Subarray](https://leetcode.com/problems/maximum-subarray/)| [Swift](./DP/MaximumSubarray.swift)| Medium| O(n)| O(1)|
@@ -175,3 +182,25 @@
 [Top K Frequent Elements](https://leetcode.com/problems/top-k-frequent-elements/)| [Swift](./Array/TopKFrequentElements.swift)| Medium| O(nlogn)| O(n)|
 [Meeting Rooms](https://leetcode.com/problems/meeting-rooms/)| [Swift](./Sort/MeetingRooms.swift)| Easy| O(nlogn)| O(1)|
 [Merge Intervals](https://leetcode.com/problems/merge-intervals/)| [Swift](./Sort/MergeIntervals.swift)| Hard| O(nlogn)| O(n)|
+
+## Google
+| Title | Solution | Difficulty | Frequency |
+| ----- | -------- | ---------- | --------- |
+[Plus One](https://leetcode.com/problems/plus-one/)| [Swift](./Math/PlusOne.swift)| Easy| ★★★★★★|
+[Number of Islands](https://leetcode.com/problems/number-of-islands/)| [Swift](./DFS/NumberofIslands.swift)| Medium| ★★★★|
+[Summary Ranges](https://leetcode.com/problems/summary-ranges/)| [Swift](./Array/SummaryRanges.swift)| Medium| ★★★★|
+[Perfect Squares](https://leetcode.com/problems/perfect-squares/)| [Swift](./DP/PerfectSquares.swift)| Medium| ★★★★|
+[Merge Intervals](https://leetcode.com/problems/merge-intervals/)| [Swift](./Sort/MergeIntervals.swift)| Hard| ★★★|
+[Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)| [Swift](./Stack/ValidParentheses.swift)| Easy| ★★★|
+[Merge k Sorted Lists](https://leetcode.com/problems/merge-k-sorted-lists/)| [Swift](./LinkedList/MergeKSortedLists.swift)| Hard| ★★|
+[Find Peak Element](https://leetcode.com/problems/find-peak-element/)| [Swift](./Search/FindPeakElement.swift)| Medium| ★★|
+[Spiral Matrix](https://leetcode.com/problems/spiral-matrix/)| [Swift](./Array/SpiralMatrix.swift)| Medium| ★★|
+[Sliding Window Maximum ](https://leetcode.com/problems/sliding-window-maximum/)| [Swift](./Array/SlidingWindowMaximum.swift)| Hard| ★★|
+[Power of Two](https://leetcode.com/problems/power-of-two/)| [Swift](./Math/PowerTwo.swift)| Easy| ★★|
+
+## Facebook
+
+
+
+
+