Problem_0341_NestedIterator.cc

#include <iostream>
#include <stack>
#include <vector>

using namespace std;

class NestedInteger
{
 public:
  // Return true if this NestedInteger holds a single integer, rather than a nested list.
  bool isInteger() const;

  // 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
  int getInteger() const;

  // 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
  const vector<NestedInteger> &getList() const;
};

class NestedIterator
{
 private:
  vector<int> vals;
  vector<int>::iterator cur;

  void dfs(const vector<NestedInteger> &nestedList)
  {
    for (auto &nest : nestedList)
    {
      if (nest.isInteger())
      {
        vals.push_back(nest.getInteger());
      }
      else
      {
        dfs(nest.getList());
      }
    }
  }

 public:
  NestedIterator(vector<NestedInteger> &nestedList)
  {
    dfs(nestedList);
    cur = vals.begin();
  }

  int next() { return *cur++; }

  bool hasNext() { return cur != vals.end(); }
};

/**
 * Your NestedIterator object will be instantiated and called as such:
 * NestedIterator i(nestedList);
 * while (i.hasNext()) cout << i.next();
 */