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# 281.Zigzag-Iterator

## 281. Zigzag Iterator

## 题目地址

<https://leetcode.com/problems/zigzag-iterator/>

## 题目描述

```
Given two 1d vectors, implement an iterator to return their elements alternately.

Example:
Input:
v1 = [1,2]
v2 = [3,4,5,6] 
Output: [1,3,2,4,5,6]
Explanation: By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,3,2,4,5,6].

Follow up:
What if you are given k 1d vectors? How well can your code be extended to such cases?

Clarification for the follow up question:
The "Zigzag" order is not clearly defined and is ambiguous for k > 2 cases. If "Zigzag" does not look right to you, replace "Zigzag" with "Cyclic". For example:

Input:
[1,2,3]
[4,5,6,7]
[8,9]

Output: [1,4,8,2,5,9,3,6,7].
```

## 代码

### Approach #1

```java
public class ZigzagIterator {
    LinkedList<Iterator> list;
  public ZigzagIterator(List<Integer> v1, List<Integer> v2) {
        list = new LinkedList<Iterator>();
    if (!v1.isEmpty()) list.add(v1.iterator());
    if (!v2.isEmpty()) list.add(v2.iterator());
  }

  public int next() {
        Iterator poll = list.remove(); // 头
    int result = (Integer) poll.next();
    if (poll.hasNext) list.add(poll);
    return result;
  }

  public boolean hasNext() {
        return !list.isEmpty();
  }
}

/**
 * Your ZigzagIterator object will be instantiated and called as such:
 * ZigzagIterator i = new ZigzagIterator(v1, v2);
 * while (i.hasNext()) v[f()] = i.next();
 */
```