Update 0617.合并二叉树.md

添加 Go 的迭代版本

Author: wathenjiang

problems/0617.合并二叉树.md

@@ -426,6 +426,46 @@ func mergeTrees(root1 *TreeNode, root2 *TreeNode) *TreeNode {
     root1.Right = mergeTrees(root1.Right, root2.Right)
     return root1
 }
+
+// 迭代版本
+func mergeTrees(root1 *TreeNode, root2 *TreeNode) *TreeNode {
+    queue := make([]*TreeNode,0)
+    if root1 == nil{
+        return root2
+    }
+    if root2 == nil{
+        return root1
+    }
+    queue = append(queue,root1)
+    queue = append(queue,root2)
+
+    for size:=len(queue);size>0;size=len(queue){
+        node1 := queue[0]
+        queue = queue[1:]
+        node2 := queue[0]
+        queue = queue[1:]
+        node1.Val += node2.Val
+        // 左子树都不为空
+        if node1.Left != nil && node2.Left != nil{
+            queue = append(queue,node1.Left)
+            queue = append(queue,node2.Left)
+        }
+        // 右子树都不为空
+        if node1.Right !=nil && node2.Right !=nil{
+            queue = append(queue,node1.Right)
+            queue = append(queue,node2.Right)
+        }
+        // 树 1 的左子树为 nil，直接接上树 2 的左子树
+        if node1.Left == nil{
+            node1.Left = node2.Left
+        }
+        // 树 1 的右子树为 nil，直接接上树 2 的右子树
+        if node1.Right == nil{
+            node1.Right = node2.Right
+        }
+    }
+    return root1
+}
 ```
 
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