Flatten Nested List Iterator
Total Accepted: 723 Total Submissions: 3985 Difficulty: Medium
Given a nested list of integers, implement an iterator to flatten it.
Each element is either an integer, or a list -- whose elements may also be integers or other lists.
Example 1:
Given the list [[1,1],2,[1,1]],
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,1,2,1,1].
Example 2:
Given the list [1,[4,[6]]],
By calling next repeatedly until hasNext returns false, the order of elements returned by next should be: [1,4,6].
思路
- 这道题看上去似曾相似,果然好像做过一道题叫做 Nested List Weight Sum
- 所以我这道题一来也直接做了递归
- 没想出来更好的办法,想了一个while把自己绕进去了,应该用stack是可以做的
public class NestedIterator implements Iterator<Integer> {
private List<Integer> list = new ArrayList<Integer>();
private int size;
private int iterate = 0;
public NestedIterator(List<NestedInteger> nestedList) {
dfs(nestedList);
size = list.size();
}
public void dfs(List<NestedInteger> nestedList) {
if (nestedList == null) {
return;
}
int size = nestedList.size();
for (int i = 0; i < size; i++) {
NestedInteger cur = nestedList.get(i);
if (cur.isInteger()) {
list.add(cur.getInteger());
} else {
dfs(cur.getList());
}
}
}
@Override
public Integer next() {
return list.get(iterate++);
}
@Override
public boolean hasNext() {
return iterate < size;
}
}