Flatten Nested List Iterator

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This topic means to implement an iterator. There is a way to do this online.

 Public  class nestediterator implements Iterator<Integer> {      int Index=0; List<integer> Vals; PublicNestediterator (list<nestedinteger> nestedlist) {vals = parser (nestedlist); } Publiclist<integer> parser (list<nestedinteger> nestedlist) {list<integer> res =NewArraylist<integer> (); for(Nestedinteger n:nestedlist) {if(N.isinteger ())              {Res.add (N.getinteger ()); }Else{Res.addall (Parser (N.getlist ())); }          }returnRes } PublicInteger Next () {if(Index< Vals.size ()) {intval = Vals.get (Index);Index++;returnVal }Else{return-1; }      } Public BooleanHasnext () {return! (Index>= vals.size ()); }  }

This method is simple and rough. However, this is not an ideal implementation, because this implementation causes memory usage to increase by one-fold. My own way of achieving this is

Import Java.util.deque;import java.util.iterator;import java.util.linkedlist;import java.util.List;InterfaceNestedinteger {//@return True if this nestedinteger holds a single integer, rather than a nested list.       PublicBooleanIsinteger();//@return The single integer which this nestedinteger holds, if it holds a single integer      //Return NULL if this nestedinteger holds a nested list       PublicIntegerGetinteger();//@return The nested list that this nestedinteger holds, if it holds a nested list      //Return NULL if this nestedinteger holds a single integer       PublicList<nestedinteger>getList(); } Public classNestediterator implements Iterator<integer> {StaticDeque<list<nestedinteger>> stack=NewLinkedlist<list<nestedinteger>> ();StaticDeque<integer> stackindex=NewLinkedlist<integer> (); List<nestedinteger> nestedlist; Public Nestediterator(list<nestedinteger> nestedlist)        {Stack.add (nestedlist); Stackindex.add (0); } @Override PublicIntegerNext() {intCurrindex=stackindex.polllast ();        List<nestedinteger> Currlist=stack.peeklast (); Nestedinteger currele=currlist.Get(Currindex);if(!currele.isinteger ())            {Stack.addlast (Currele.getlist ()); Stackindex.addlast (0);returnNext (); }intResult=currele.getinteger ();if(currindex+1>=currlist.size ()) {stack.polllast (); }Else{Stackindex.addlast (currindex+1); }returnResult } @Override PublicBooleanHasnext() {if(stack.size () = =0)        {return false; }Else{intCurrindex=stackindex.peeklast (); List<nestedinteger> Currlist=stack.peeklast ();if(!currlist.Get(Currindex). Isinteger () &&currlist.Get(Currindex). GetList () = =NULL) {stack.polllast ();if(currindex+1>=currlist.size ()) {stackindex.polllast (); }Else{stackindex.polllast (); Stackindex.addlast (currindex+1); }returnHasnext (); }        }return true; }}/** * Your Nestediterator object would be instantiated and called as such: * nestediterator i = new Nestediterator (nest Edlist); * while (I.hasnext ()) v[f ()] = I.next (); */

But. This algorithm can not handle [1,2,3,[]] This situation, it may be I did not understand [] the expression in the OJ. But as long as there is no such situation, the code is working properly

Flatten Nested List Iterator