"Leetcode-Interview algorithm classic-java implementation" "102-binary Tree Level order traversal (binary sequence Traversal)"

"102-binary Tree Level Order traversal (binary tree sequence traversal)" "leetcode-Interview algorithm classic-java Implementation" "All topics Directory Index" Original Question

Given a binary tree, return the level order traversal of its nodes ' values. (ie, from left-to-right, level by level).
For example:
Given binary Tree {3,9,20,#,#,15,7},

    3     9  20    /     15   7

Return its level order traversal as:

[  [3],  [9,20],  [15,7]]

Main Topic

Given a binary tree, output the nodes of each of its layers.

Thinking of solving problems

Use two queues, one to save the current processing layer, and one to save the next one to process. It's all done at every level.

Code Implementation

Tree Node class

publicclass TreeNode {    int val;    TreeNode left;    TreeNode right;    TreeNode(int x) {        val = x;    }}

Algorithm implementation class

Import Java.util.arraylist;import java.util.deque;import Java.util.linkedlist;import Java.util.List;public class Solution {public list<list<integer>> levelorder (TreeNode root) {list<list<integer>> re Sult = new arraylist<> ();if(root = null) {returnResult        } deque<treenode> cur = new linkedlist<> (); Deque<treenode> Sub = new linkedlist<> ();Deque<treenode> exc;        TreeNode node; Cur.addlast (root); while(!cur.isempty ()) {list<integer> layout = new linkedlist<> (); while(!cur.isempty ())                {node = Cur.removefirst (); Layout.add (Node.val);if(Node.left! = null) { Sub. AddLast (node.left);}if(node.right! = null) { Sub. AddLast (node.right);}} exc = cur; Cur = Sub;             Sub = exc;Result.add (layout); }returnResult }}

Evaluation Results

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leetcode-Interview Algorithm classic-java implementation "102-binary Tree Level order traversal (binary sequence traversal)"