Add 1641 & 1679

Author: TerryHuangHD

Array/MaxNumberOfK-SumPairs.swift

@@ -0,0 +1,16 @@
+class Solution {
+    func maxOperations(_ nums: [Int], _ k: Int) -> Int {
+        var rest = [Int: Int]()
+        var result = 0
+        for num in nums {
+            if let count = rest[k-num], count > 0 {
+                rest[k-num] = count-1
+                result += 1
+            } else {
+                rest[num, default: 0] += 1
+            }
+        }
+        
+        return result
+    }
+}

DP/CountSortedVowelStrings.swift

@@ -0,0 +1,21 @@
+class Solution {
+    func countVowelStrings(_ n: Int) -> Int {
+        var curr = [0, 0, 0, 0, 1]
+        
+        for _ in 1..<n {
+            var next = [Int]()
+            var sum = 0
+            for x in (0..<curr.count).reversed() {
+                sum += curr[x]
+                next.insert(sum, at:0)
+            }
+            curr = next
+        }
+        
+        var result = 0
+        for x in 0..<curr.count {
+            result += curr[x] * (x+1)
+        }
+        return result
+    }
+}

README.md

@@ -42,6 +42,7 @@
 ## Array
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
+[Max Number of K-Sum Pairs](https://leetcode.com/problems/max-number-of-k-sum-pairs/)|[Swift](./Array/MaxNumberOfK-SumPairs.swift)| Medium| O(n)| O(n)|
 [Check Array Formation Through Concatenation](https://leetcode.com/problems/check-array-formation-through-concatenation/)|[Swift](./Array/CheckArrayFormationThroughConcatenation.swift)| Easy| O(nlogn)| O(n)|
 [Verify an Alien Dictionary](https://leetcode.com/problems/verifying-an-alien-dictionary/)|[Swift](Array/VerifyingAlienDictionary.swift)| Easy| O(n)| O(n)|
 [Sort Array By Parity](https://leetcode.com/problems/sort-array-by-parity/)|[Swift](./Array/SortArrayByParity.swift)| Easy| O(n)| O(n)|
@@ -225,6 +226,7 @@
 ## Dynamic programming
 | Title | Solution | Difficulty | Time | Space |
 | ----- | -------- | ---------- | ---- | ----- |
+[Count Sorted Vowel Strings](https://leetcode.com/problems/count-sorted-vowel-strings/) | [Swift](./DP/CountSortedVowelStrings.swift)	| Medium| O(n)| O(n)|
 [Minimum Operations to Reduce X to Zero](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/) | [Swift](./DP/MinimumOperationsToReduceXToZero.swift)	| Medium| O(n)| O(n)|
 [Boats to Save People](https://leetcode.com/problems/boats-to-save-people/) | [Swift](./DP/BoatsToSavePeople.swift)	| Medium| O(nlogn)| O(n)|
 [Nested List Weight Sum](https://leetcode.com/problems/nested-list-weight-sum/)| [Swift](./DP/NestedListWeightSum.swift)| Easy| O(n)| O(1)|
@@ -548,7 +550,9 @@
 ## Problem Status
 | Solution | Number | Title | Difficulty |
 | -------- | ------ | ----- | ---------- |
+| [Swift](./Array/MaxNumberOfK-SumPairs.swift)	|	1679	|	[Max Number of K-Sum Pairs](https://leetcode.com/problems/max-number-of-k-sum-pairs/)	| Medium	|
 | [Swift](./DP/MinimumOperationsToReduceXToZero.swift)	|	1658	|	[Minimum Operations to Reduce X to Zero](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/)	| Medium	|
+| [Swift](./DP/CountSortedVowelStrings.swift)	|	1641	|	[Count Sorted Vowel Strings](https://leetcode.com/problems/count-sorted-vowel-strings/)	| Medium	|
 | [Swift](./Array/CheckArrayFormationThroughConcatenation.swift)	|	1640	|	[Check Array Formation Through Concatenation](https://leetcode.com/problems/check-array-formation-through-concatenation/)	| Easy	|
 | [Swift](./LinkedList/PseudoPalindromicPathsInABinaryTree.swift)	|	1457	|	[Pseudo-Palindromic Paths in a Binary Tree](https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree/)	| Medium	|
 | [Swift](./BFS/JumpGameIV.swift)	|	1345	|	[Jump Game IV](https://leetcode.com/problems/jump-game-iv/)	| Hard	|