Flatten 2D Vector

Implement a iterator to flatten a 2d vector.

For example, Given 2d vector =

[  [1,2],  [3],  [4,5,6]] 

By calling next repeatedly until Hasnext returns false, the order of elements returned by next should is: [1,2,3,4,5,6] .

Analysis: 1190000003791233

An array is used to represent the iterator for each list, and then a variable is recorded to indicate that the first iterator is currently used.

1  Public classvector2d {2 3List<iterator<integer>>its ;4     intCurr =0;5 6      PublicVector2d (list<list<integer>>vec2d) {7          This. its =NewArraylist<iterator<integer>>();8          for(list<integer>l:vec2d) {9             //add only non-null iterators to the arrayTen             if(L.size () >0) { One                  This. Its.add (L.iterator ()); A             } -         } -     } the  -      Public intNext () { -Integer res = its.Get(Curr). Next (); -         //if the iterator is finished, switch to the next +         if(!its.Get(Curr). Hasnext ()) { -curr++; +         } A         returnRes; at     } -  -      PublicBoolean hasnext () { -         returnCurr < Its.size () && its.Get(Curr). Hasnext (); -     } -}

Flatten 2D Vector