Simple recursive solution in Java


  • 0
    I
    /**
     * // This is the interface that allows for creating nested lists.
     * // You should not implement it, or speculate about its implementation
     * public interface NestedInteger {
     *
     *     // @return true if this NestedInteger holds a single integer, rather than a nested list.
     *     public boolean isInteger();
     *
     *     // @return the single integer that this NestedInteger holds, if it holds a single integer
     *     // Return null if this NestedInteger holds a nested list
     *     public Integer getInteger();
     *
     *     // @return the nested list that this NestedInteger holds, if it holds a nested list
     *     // Return null if this NestedInteger holds a single integer
     *     public List<NestedInteger> getList();
     * }
     */
    public class NestedIterator implements Iterator<Integer> {
        
        private List<NestedInteger> data;
        private NestedIterator iterator;
        private int pos;
        
        public NestedIterator(List<NestedInteger> nestedList) {
            this.data = nestedList;
        }
    
        @Override
        public Integer next() {
            if(data.get(pos).isInteger()) {
               return data.get(pos++).getInteger();
            }
            
            return iterator.next();
        }
    
        @Override
        public boolean hasNext() {
            while(pos < data.size()) {
                if(data.get(pos).isInteger()) {
                    return true;
                } 
                
                if(null == iterator) {
                    iterator = new NestedIterator(data.get(pos).getList());
                }
                
                if(iterator.hasNext()) {
                    return true;
                }
                
                iterator = null;
                pos++;
            }
            
            
            return false;
        }
    }
    
    /**
     * Your NestedIterator object will be instantiated and called as such:
     * NestedIterator i = new NestedIterator(nestedList);
     * while (i.hasNext()) v[f()] = i.next();
     */
    

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