89 lines
2.2 KiB
Java
89 lines
2.2 KiB
Java
//给你一个二叉树，请你返回其按 层序遍历 得到的节点值。 （即逐层地，从左到右访问所有节点）。
|
|
//
|
|
//
|
|
//
|
|
// 示例：
|
|
//二叉树：[3,9,20,null,null,15,7],
|
|
//
|
|
//
|
|
// 3
|
|
// / \
|
|
// 9 20
|
|
// / \
|
|
// 15 7
|
|
//
|
|
//
|
|
// 返回其层序遍历结果：
|
|
//
|
|
//
|
|
//[
|
|
// [3],
|
|
// [9,20],
|
|
// [15,7]
|
|
//]
|
|
//
|
|
// Related Topics 树 广度优先搜索 二叉树
|
|
// 👍 945 👎 0
|
|
|
|
package leetcode.editor.cn;
|
|
|
|
import com.code.leet.entiy.TreeNode;
|
|
|
|
import java.util.ArrayList;
|
|
import java.util.LinkedList;
|
|
import java.util.List;
|
|
import java.util.Queue;
|
|
|
|
//102:二叉树的层序遍历
|
|
public class BinaryTreeLevelOrderTraversal {
|
|
public static void main(String[] args) {
|
|
//测试代码
|
|
Solution solution = new BinaryTreeLevelOrderTraversal().new Solution();
|
|
}
|
|
//力扣代码
|
|
//leetcode submit region begin(Prohibit modification and deletion)
|
|
|
|
/**
|
|
* 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) {
|
|
if (root == null) {
|
|
return new ArrayList<>();
|
|
}
|
|
Queue<TreeNode> queue = new LinkedList<>();
|
|
List<List<Integer>> result = new ArrayList<>();
|
|
queue.add(root);
|
|
while (!queue.isEmpty()) {
|
|
int size = queue.size();
|
|
List<Integer> list = new ArrayList<>();
|
|
for (int i = 0; i < size; i++) {
|
|
TreeNode temp = queue.poll();
|
|
list.add(temp.val);
|
|
if (temp.left != null) {
|
|
queue.add(temp.left);
|
|
}
|
|
if (temp.right != null) {
|
|
queue.add(temp.right);
|
|
}
|
|
}
|
|
result.add(list);
|
|
}
|
|
return result;
|
|
}
|
|
}
|
|
//leetcode submit region end(Prohibit modification and deletion)
|
|
|
|
} |