flatten-nested-list-iterator.js

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * function NestedInteger() {
 *
 *     Return true if this NestedInteger holds a single integer, rather than a nested list.
 *     @return {boolean}
 *     this.isInteger = function() {
 *         ...
 *     };
 *
 *     Return the single integer that this NestedInteger holds, if it holds a single integer
 *     Return null if this NestedInteger holds a nested list
 *     @return {integer}
 *     this.getInteger = function() {
 *         ...
 *     };
 *
 *     Return the nested list that this NestedInteger holds, if it holds a nested list
 *     Return null if this NestedInteger holds a single integer
 *     @return {NestedInteger[]}
 *     this.getList = function() {
 *         ...
 *     };
 * };
 */
/**
 * @constructor
 * @param {NestedInteger[]} nestedList
 */
var stack = [];
var NestedIterator = function (nestedList) {
    for (var i in nestedList) {
        if (Number.isInteger(nestedList[i])) {
            stack.unshift(nestedList[i]);
        } else {
            NestedIterator(nestedList[i]);
        }
    }

    // Time Complexity: O(n)
};


/**
 * @this NestedIterator
 * @returns {boolean}
 */
NestedIterator.prototype.hasNext = function () {
    return stack.length > 0;
    // Time Complexity: O(1)
};

/**
 * @this NestedIterator
 * @returns {integer}
 */
NestedIterator.prototype.next = function () {
    return stack.pop();
    // Time Complexity: O(1)
};

/**
 * Your NestedIterator will be called like this:
 * var i = new NestedIterator(nestedList), a = [];
 * while (i.hasNext()) a.push(i.next());
 */