From 1dd57ca07df04e6d9af8ec4067447651d9433de9 Mon Sep 17 00:00:00 2001
From: Joshua <47053655+Joshua-Lu@users.noreply.github.com>
Date: Fri, 14 May 2021 01:19:18 +0800
Subject: [PATCH] =?UTF-8?q?Update=200617.=E5=90=88=E5=B9=B6=E4=BA=8C?=
 =?UTF-8?q?=E5=8F=89=E6=A0=91.md?=
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添加 0617.合并二叉树 Java版本
---
 problems/0617.合并二叉树.md | 53 ++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/problems/0617.合并二叉树.md b/problems/0617.合并二叉树.md
index adc0703b..520a7384 100644
--- a/problems/0617.合并二叉树.md
+++ b/problems/0617.合并二叉树.md
@@ -256,7 +256,60 @@ public:
 
 
 Java：
+```Java
+class Solution {
+    // 递归
+    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
+        if (root1 == null) {
+            return root2;
+        }
+        if (root2 == null) {
+            return root1;
+        }
+        root1.val += root2.val;
+        root1.left = mergeTrees(root1.left, root2.left);
+        root1.right = mergeTrees(root1.right, root2.right);
+        return root1;
+    }
+}
 
+class Solution {
+   // 迭代
+    public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {
+        if (root1 == null) {
+            return root2;
+        }
+        if (root2 == null) {
+            return root1;
+        }
+        Stack<TreeNode> stack = new Stack<>();
+        stack.push(root2);
+        stack.push(root1);
+        while (!stack.isEmpty()) {
+            TreeNode node1 = stack.pop();
+            TreeNode node2 = stack.pop();
+            node1.val += node2.val;
+            if (node2.right != null && node1.right != null) {
+                stack.push(node2.right);
+                stack.push(node1.right);
+            } else {
+                if (node1.right == null) {
+                    node1.right = node2.right;
+                }
+            }
+            if (node2.left != null && node1.left != null) {
+                stack.push(node2.left);
+                stack.push(node1.left);
+            } else {
+                if (node1.left == null) {
+                    node1.left = node2.left;
+                }
+            }
+        }
+        return root1;
+    }
+}
+```
 
 Python：