251.Flatten 2D Vector

/** 251.Flatten 2D Vector * 2016-6-20 by Mingyang *-------Boolean hasnext () * Returns true if the iteration have more E  Lements. * (in other words, returns True if Next () would return a element rather than throwing an exception.) *-------E Next () *returns the next element in the iteration. *returns: *the next element in the iteration *throws: *nosuchelementexception-if The iteration have no more elements * key questions The problem is to master the use of good iterator*/classvector2d {Privateiterator<list<integer>> row =NULL; Privateiterator<integer> col =NULL;  PublicVector2d (list<list<integer>>vec2d) {Row=Vec2d.iterator (); if(Row.hasnext ()) Col=Row.next (). iterator (); }       Public intNext () {intLastvalue =Col.next (); returnLastvalue; }       Public BooleanHasnext () {if(col = =NULL) {              return false; }          if(Col.hasnext ()) {return true; } Else {               while(Row.hasnext ()) {col=Row.next (). iterator (); if(Col.hasnext ())return true; }              return false; }      }  

251.Flatten 2D Vector