Merge branch 'master' of github.com:partho-maple/coding-interview-gym

* 'master' of github.com:partho-maple/coding-interview-gym:
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Author: partho-maple

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/138_Copy_List_with_Random_Pointer.swift

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+import Foundation
+

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/341_Flatten_Nested_List_Iterator.swift

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+/**
+ * // This is the interface that allows for creating nested lists.
+ * // You should not implement it, or speculate about its implementation
+ * class NestedInteger {
+ *     // Return true if this NestedInteger holds a single integer, rather than a nested list.
+ *     public func isInteger() -> Bool
+ *
+ *     // Return the single integer that this NestedInteger holds, if it holds a single integer
+ *     // The result is undefined if this NestedInteger holds a nested list
+ *     public func getInteger() -> Int
+ *
+ *     // Set this NestedInteger to hold a single integer.
+ *     public func setInteger(value: Int)
+ *
+ *     // Set this NestedInteger to hold a nested list and adds a nested integer to it.
+ *     public func add(elem: NestedInteger)
+ *
+ *     // Return the nested list that this NestedInteger holds, if it holds a nested list
+ *     // The result is undefined if this NestedInteger holds a single integer
+ *     public func getList() -> [NestedInteger]
+ * }
+ */
+
+class NestedIterator {
+
+    var nestedListStack = [([NestedInteger], Int)]()
+
+    init(_ nestedList: [NestedInteger]) {
+        self.nestedListStack.append((nestedList, 0))
+    }
+
+    func next() -> Int {
+        let (nestedList, currentIndex) = nestedListStack.removeLast()
+        let result = nestedList[currentIndex].getInteger()
+        nestedListStack.append((nestedList, currentIndex + 1))
+        return result
+    }
+
+    func hasNext() -> Bool {
+        while !nestedListStack.isEmpty {
+            let (nestedList, currentIndex) = nestedListStack.last!
+            if currentIndex >= nestedList.count {
+                nestedListStack.removeLast()
+            } else {
+                if nestedList[currentIndex].isInteger() {
+                    return true
+                } else {
+                    nestedListStack[nestedListStack.count - 1] = (nestedList, currentIndex + 1)
+                    nestedListStack.append((nestedList[currentIndex].getList(), 0))
+                }
+            }
+        }
+        return false
+    }
+}
+
+/**
+ * Your NestedIterator object will be instantiated and called as such:
+ * let obj = NestedIterator(nestedList)
+ * let ret_1: Int = obj.next()
+ * let ret_2: Bool = obj.hasNext()
+ */