[Array] Add solutions to Two Sum II and III

Author: soapyigu

Array/TwoSumII.swift

@@ -0,0 +1,28 @@
+/**
+ * Question Link: https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/
+ * Primary idea: Two pointers -- left moves forward and right moves backward to meet the right two sum.
+ *
+ * Time Complexity: O(n), Space Complexity: O(n)
+ */
+
+class TwoSumII {
+    func twoSum(_ numbers: [Int], _ target: Int) -> [Int] {
+        if numbers.count <= 1 {
+            return [Int]()
+        }
+        
+        var left = 0, right = numbers.count - 1
+        
+        while left < right {
+            if numbers[left] + numbers[right] < target {
+                left += 1
+            } else if numbers[left] + numbers[right] > target {
+                right -= 1
+            } else {
+                return [left + 1, right + 1]
+            }
+        }
+        
+        return [Int]()
+    }
+}

Array/TwoSumIII.swift

@@ -0,0 +1,33 @@
+/**
+ * Question Link: https://leetcode.com/problems/two-sum-iii-data-structure-design/
+ * 
+ * Note: This answer offers a different solution instead of the one requsted by leetcode.
+ *       Assuming the use case is find API is called many more times than add API.
+ *       For the answer accepted by leetcode, you could reference Two Sum and Two Sum II.
+ *
+ * Primary idea: Use a set for all two sums value, and array to keep all numbers added.
+ * Time Complexity: add - O(n), find - O(1), Space Complexity: O(n)
+ */
+
+class TwoSumIII {
+
+    var nums: [Int]
+    var twoSums: Set<Int>()
+    
+    /** Initialize your data structure here. */
+    init() {
+        nums = [Int]()
+        twoSums = Set<Int>()
+    }
+    
+    /** Add the number to an internal data structure.. */
+    func add(_ number: Int) {
+        nums.forEach { twoSums.insert($0 + number) }
+        nums.append(number)
+    }
+    
+    /** Find if there exists any pair of numbers which sum is equal to the value. */
+    func find(_ value: Int) -> Bool {
+        return twoSums.contains(value)
+    }
+}

README.md

@@ -4,7 +4,7 @@
 ![Leetcode](./logo.png?style=centerme)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 304 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
+[Problem Status](#problem-status) shows the latest progress to all 1000+ questions. Currently we have 306 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them.
 
 ## Contributors
 
@@ -61,6 +61,8 @@
 [Strobogrammatic Number](https://leetcode.com/problems/strobogrammatic-number/)| [Swift](./Array/StrobogrammaticNumber.swift)| Easy| O(n)| O(1)|
 [Can Place Flowers](https://leetcode.com/problems/can-place-flowers/)| [Swift](./Array/CanPlaceFlowers.swift)| Easy| O(n)| O(1)|
 [Two Sum](https://leetcode.com/problems/two-sum/)| [Swift](./Array/TwoSum.swift)| Easy| O(n)| O(n)|
+[Two Sum II - Input array is sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/)| [Swift](./Array/TwoSumII.swift)| Easy| O(n)| O(1)|
+[Two Sum III - Data structure design](https://leetcode.com/problems/two-sum-iii-data-structure-design/)| [Swift](./Array/TwoSumIII.swift)| Easy| O(n)| O(1)|
 [Two Sum Less Than K](https://leetcode.com/problems/two-sum-less-than-k/)| [Swift](./Array/TwoSumLessThanK.swift)| Easy| O(nlogn)| O(n)|
 [3Sum](https://leetcode.com/problems/3sum/)| [Swift](./Array/ThreeSum.swift)| Medium| O(n^2)| O(nC3)|
 [3Sum Closest](https://leetcode.com/problems/3sum-closest/)| [Swift](./Array/ThreeSumClosest.swift)| Medium| O(n^2)| O(nC3)|
@@ -713,10 +715,10 @@
 |		|	173	|	[Binary Search Tree Iterator](https://oj.leetcode.com/problems/binary-search-tree-iterator/)	| Medium	|
 |	[Swift](./Math/FactorialTrailingZeroes.swift)	|	172	|	[Factorial Trailing Zeroes](https://oj.leetcode.com/problems/factorial-trailing-zeroes/)	| Easy	|
 |	[Swift](./Math/ExcelSheetColumnNumber.swift)	|	171	|	[Excel Sheet Column Number](https://oj.leetcode.com/problems/excel-sheet-column-number/)	| Easy	|
-|	|	170	|	[Two Sum III - Data structure design](https://oj.leetcode.com/problems/two-sum-iii-data-structure-design/) ♥	| Easy	|
-| [Swift](./Array/MajorityElement.swift)  |	169	|	[Majority Element](https://oj.leetcode.com/problems/majority-element/)	| Easy	|
+|	[Swift](./Array/TwoSumIII.swift)	|	170	|	[Two Sum III - Data structure design](https://oj.leetcode.com/problems/two-sum-iii-data-structure-design/) ♥	| Easy	|
+| 	[Swift](./Array/MajorityElement.swift)  |	169	|	[Majority Element](https://oj.leetcode.com/problems/majority-element/)	| Easy	|
 |		|	168	|	[Excel Sheet Column Title](https://oj.leetcode.com/problems/excel-sheet-column-title/)	| Easy	|
-|		|	167	|	[Two Sum II - Input array is sorted](https://oj.leetcode.com/problems/two-sum-ii-input-array-is-sorted/) ♥	| Medium	|
+|	[Swift](./Array/TwoSumII.swift)	|	167	|	[Two Sum II - Input array is sorted](https://oj.leetcode.com/problems/two-sum-ii-input-array-is-sorted/) ♥	| Medium	|
 |	[Swift](./Math/FractionToRecurringDecimal.swift)	|	166	|	[Fraction to Recurring Decimal](https://oj.leetcode.com/problems/fraction-to-recurring-decimal/)	| Medium	|
 |		|	165	|	[Compare Version Numbers](https://oj.leetcode.com/problems/compare-version-numbers/)	| Easy	|
 |		|	164	|	[Maximum Gap](https://oj.leetcode.com/problems/maximum-gap/)	| Hard	|