[Array] add Solutions to Intersection of Two Arrays I, II

Author: Yi Gu

Array/IntersectionTwoArrays.swift

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+/**
+ * Question Link: https://leetcode.com/problems/intersection-of-two-arrays/
+ * Primary idea: Use set interact function to help
+ *
+ * Time Complexity: O(n), Space Complexity: O(n)
+ *
+ */
+
+class IntersectionTwoArrays {
+    func intersection(nums1: [Int], _ nums2: [Int]) -> [Int] {
+      return [Int](Set<Int>(nums1).intersect(nums2))
+    }
+}

Array/IntersectionTwoArraysII.swift

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+/**
+ * Question Link: https://leetcode.com/problems/intersection-of-two-arrays-ii/
+ * Primary idea: Sort and iterate to find all common elements
+ * Note: Set cannot help you to find the number of common elements; thus it is not effective
+ *
+ * Time Complexity: O(nlogn), Space Complexity: O(n)
+ *
+ */
+
+ class IntersectionTwoArraysII {
+    func intersect(nums1: [Int], _ nums2: [Int]) -> [Int] {
+        var nums1 = nums1.sort({$0 < $1})
+        var nums2 = nums2.sort({$0 < $1})
+        
+        var i = 0
+        var j = 0
+        var res = [Int]()
+        
+        while i < nums1.count && j < nums2.count {
+            if nums1[i] < nums2[j] {
+                i += 1
+            } else if nums1[i] > nums2[j] {
+                j += 1
+            } else {
+                res.append(nums1[i])
+                i += 1
+                j += 1
+            }
+        }
+        
+        return res
+    }
+}