Add solution #341

Author: JoshCrozier

README.md

@@ -265,6 +265,7 @@
 334|[Increasing Triplet Subsequence](./0334-increasing-triplet-subsequence.js)|Medium|
 337|[House Robber III](./0337-house-robber-iii.js)|Medium|
 338|[Counting Bits](./0338-counting-bits.js)|Easy|
+341|[Flatten Nested List Iterator](./0341-flatten-nested-list-iterator.js)|Medium|
 342|[Power of Four](./0342-power-of-four.js)|Easy|
 344|[Reverse String](./0344-reverse-string.js)|Easy|
 345|[Reverse Vowels of a String](./0345-reverse-vowels-of-a-string.js)|Easy|

solutions/0341-flatten-nested-list-iterator.js

@@ -0,0 +1,64 @@
+/**
+ * 341. Flatten Nested List Iterator
+ * https://leetcode.com/problems/flatten-nested-list-iterator/
+ * Difficulty: Medium
+ *
+ * You are given a nested list of integers nestedList. Each element is either an integer or a list
+ * whose elements may also be integers or other lists. Implement an iterator to flatten it.
+ *
+ * Implement the NestedIterator class:
+ * - NestedIterator(List<NestedInteger> nestedList) Initializes the iterator with the nested list
+ *   nestedList.
+ * - int next() Returns the next integer in the nested list.
+ * - boolean hasNext() Returns true if there are still some integers in the nested list and false
+ *   otherwise.
+ *
+ * Your code will be tested with the following pseudocode:
+ * initialize iterator with nestedList
+ * res = []
+ * while iterator.hasNext()
+ *   append iterator.next() to the end of res
+ * return res
+ *
+ * If res matches the expected flattened list, then your code will be judged as correct.
+ */
+
+/**
+ * @constructor
+ * @param {NestedInteger[]} nestedList
+ */
+var NestedIterator = function(nestedList) {
+  this.stack = [];
+  this.flatten(nestedList);
+};
+
+/**
+ * @this NestedIterator
+ * @param {NestedInteger[]} nestedList
+ * @returns {void}
+ */
+NestedIterator.prototype.flatten = function(list) {
+  for (let i = list.length - 1; i >= 0; i--) {
+    this.stack.push(list[i]);
+  }
+};
+
+/**
+ * @this NestedIterator
+ * @returns {boolean}
+ */
+NestedIterator.prototype.hasNext = function() {
+  while (this.stack.length > 0 && !this.stack[this.stack.length - 1].isInteger()) {
+    const nested = this.stack.pop().getList();
+    this.flatten(nested);
+  }
+  return this.stack.length > 0;
+};
+
+/**
+ * @this NestedIterator
+ * @returns {integer}
+ */
+NestedIterator.prototype.next = function() {
+  return this.stack.pop().getInteger();
+};