ok

NoteXYX · NoteXYX · commit e509fa3fe2e2 · 2020-09-06T23:57:55.000+08:00
diff --git a/src/com/leetcode/Main107.java b/src/com/leetcode/Main107.java
@@ -0,0 +1,40 @@
+package com.leetcode;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+/**
+ * 107. 二叉树的层次遍历 II
+ * 给定一个二叉树，返回其节点值自底向上的层次遍历。 （即按从叶子节点所在层到根节点所在的层，逐层从左向右遍历）
+ */
+public class Main107 {
+    public class TreeNode {
+        int val;
+        TreeNode left;
+        TreeNode right;
+        TreeNode(int x) { val = x; }
+    }
+    public List<List<Integer>> levelOrderBottom(TreeNode root) {
+        List<List<Integer>> res = new LinkedList<>();
+        if(root == null)
+            return res;
+        Queue<TreeNode> queue = new LinkedList<>();
+        queue.offer(root);
+        while(!queue.isEmpty()) {
+            int size = queue.size();
+            List<Integer> tmp = new ArrayList<>();
+            for(int i = 0; i < size; i++) {
+                TreeNode node = queue.poll();
+                tmp.add(node.val);
+                if(node.left != null)
+                    queue.offer(node.left);
+                if(node.right != null)
+                    queue.offer(node.right);
+            }
+            res.add(0, tmp);
+        }
+        return res;
+    }
+}
