Merge pull request #630 from binglu18/master

补充 0102.二叉树的层序遍历.md java方法二

problems/0102.二叉树的层序遍历.md

@@ -1072,6 +1072,32 @@ class Solution {
 }
 ```
 
+```java 
+//方法二：用一个max变量来保存最大值
+class Solution {
+    public List<Integer> largestValues(TreeNode root) {
+        Queue<TreeNode> queue = new LinkedList<TreeNode>();
+        List<Integer> result = new ArrayList<>();
+        if (root != null) queue.add(root);
+	
+        while(!queue.isEmpty()){
+            int size = queue.size();
+            int max = Integer.MIN_VALUE; // 初始化为最小值
+            for(int i = 0; i < size; i++){
+                TreeNode node = queue.poll();
+                max = Math.max(node.val, max);
+                if(node.left != null)
+                    queue.add(node.left);
+                if(node.right != null)
+                    queue.add(node.right);
+            }
+            result.add(max); // 取最大值放进数组
+        }
+        return result;
+    }
+}
+```
+
 go:
 
 ```GO