LeetCode 102. 数据结构->二叉树的层序遍历(控制队列bfs
原题链接
中等
作者:
JustDoIt11
,
2023-10-31 12:33:32
,
所有人可见
,
阅读 44
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public List<List<Integer>> levelOrder(TreeNode root) {
List<List<Integer>> ans = new ArrayList<>();
if (root == null) return ans;
Queue<TreeNode> q = new LinkedList<>();
int rowNow = 1, rowNext = 0;
q.add(root);
while (!q.isEmpty()) {
List<Integer> row = new ArrayList<>();
while (rowNow -- > 0 ) {
TreeNode t = q.poll();
row.add(t.val);
if (t.left != null) {
q.add(t.left);
rowNext ++ ;
}
if (t.right != null) {
q.add(t.right);
rowNext ++ ;
}
}
ans.add(row);
rowNow = rowNext;
rowNext = 0;
}
return ans;
}
}