341. Flatten Nested List Iterator

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https://leetcode.com/problems/flatten-nested-list-iterator/discuss/80147/Simple-Java-solution-using-a-stack-with-explanation

 

 1 public class NestedIterator implements Iterator<Integer> { 2  3     Stack<NestedInteger> stack = new Stack<>(); 4     public NestedIterator(List<NestedInteger> nestedList) { 5         for(int i = nestedList.size()-1; i >= 0 ; i--){ 6             stack.push(nestedList.get(i)); 7         } 8          9     }10 11     @Override12     public Integer next() {13         return stack.pop().getInteger();14     }15 16     @Override17     public boolean hasNext() {18         while(!stack.isEmpty()){19             NestedInteger cur = stack.pop();20             if(cur.isInteger()){21                 stack.push(cur);22                 return true;23             }24             for(int i = cur.getList().size()-1; i >= 0; i--){25                 stack.push(cur.getList().get(i));26             }27         }28         return false;29     }30 }

 

341. Flatten Nested List Iterator