题目
给你一个嵌套的整型列表。请你设计一个迭代器，使其能够遍历这个整型列表中的所有整数。
列表中的每一项或者为一个整数，或者是另一个列表。其中列表的元素也可能是整数或是其他列表。
示例 1:
输入: [[1,1],2,[1,1]]
输出: [1,1,2,1,1]
解释: 通过重复调用 next 直到 hasNext 返回 false，next 返回的元素的顺序应该是: [1,1,2,1,1]。
来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/flatten-nested-list-iterator
代码
/** * // 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<Integer> vals; private Iterator<Integer> cur;
public NestedIterator(List<NestedInteger> nestedList) { vals = new ArrayList<Integer>(); dfs(nestedList); cur = vals.iterator(); }
@Override public Integer next() { return cur.next(); }
@Override public boolean hasNext() { return cur.hasNext(); }
private void dfs(List<NestedInteger> nestedList) { for (NestedInteger nest : nestedList) { if (nest.isInteger()) { vals.add(nest.getInteger()); } else { dfs(nest.getList()); } } }}
/** * 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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