add new problem 1.06

contest/src/main/java/com/github/contest/design/DesignAlternativeSolution.kt

@@ -0,0 +1,29 @@
+package com.github.contest.design
+
+/**
+ * 341. Flatten Nested List Iterator
+ * Alternative Solution
+ */
+
+class NestedIteratorAlternativeSolution(nestedList: List<NestedInteger>) {
+
+    private val stack = ArrayDeque<NestedInteger>().apply {
+        nestedList.reversed().forEach { addFirst(it) }
+    }
+
+    fun next(): Int {
+        if (!hasNext()) throw NoSuchElementException()
+        return stack.removeFirst().getInteger()!!
+    }
+
+    fun hasNext(): Boolean {
+        while (stack.isNotEmpty()) {
+            val top = stack.first()
+            if (top.isInteger()) {
+                return true
+            }
+            stack.removeFirst().getList()?.reversed()?.forEach { stack.addFirst(it) }
+        }
+        return false
+    }
+}

contest/src/main/java/com/github/contest/design/DesignLeetcode.kt

@@ -245,4 +245,49 @@ class CombinationIterator(characters: String, combinationLength: Int) {
         combine(index + 1, str, subset, store, limit)
     }
 
+}
+
+/**
+ * 341. Flatten Nested List Iterator
+ */
+
+class NestedInteger {
+
+    fun isInteger() = true
+
+    fun getInteger(): Int? {
+        return null
+    }
+
+    fun getList(): List<NestedInteger>? {
+        return null
+    }
+}
+
+class NestedIterator(nestedList: List<NestedInteger>) {
+
+    private val store = mutableListOf<Int>()
+
+    init {
+        nestedList.forEach {
+            dfs(it)
+        }
+    }
+
+    private fun dfs(obj: NestedInteger) {
+        val action = obj.getInteger()
+        if (action != null) {
+            store.add(action)
+            return
+        }
+
+        obj.getList()?.forEach {
+            dfs(it)
+        }
+    }
+
+
+    fun next(): Int = store.removeFirst()
+
+    fun hasNext(): Boolean = store.isNotEmpty()
 }