Flatten Nested List Iterator

最新推荐文章于 2021-03-23 13:34:13 发布

sjphiChina

最新推荐文章于 2021-03-23 13:34:13 发布

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分类专栏：刷遍数

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本文介绍了一种实现嵌套列表迭代器的方法，通过使用队列数据结构来平铺嵌套列表，使得能够按顺序访问所有元素。文章提供了一个具体的Java实现案例。

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/**
 * // 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> {

    Queue<Integer> queue = null;

    public NestedIterator(List<NestedInteger> nestedList) {
        queue = new LinkedList<>();
        buildQueue(queue, nestedList);
    }
    
    private void buildQueue(Queue<Integer> queue, List<NestedInteger> nestedList) {
        for (NestedInteger node: nestedList) {
            if (node.isInteger()) {
                queue.offer(node.getInteger());
            } else {
                buildQueue(queue, node.getList());
            }
        }
    }

    @Override
    public Integer next() {
        return queue.poll();
    }

    @Override
    public boolean hasNext() {
        return queue.size() != 0;
    }
}

/**
 * Your NestedIterator object will be instantiated and called as such:
 * NestedIterator i = new NestedIterator(nestedList);
 * while (i.hasNext()) v[f()] = i.next();
 */