Merge pull request #786 from Jerry-306/patch-19

新增 0617.合并二叉树   JavaScript 迭代法代码

problems/0617.合并二叉树.md

@@ -507,6 +507,8 @@ func mergeTrees(root1 *TreeNode, root2 *TreeNode) *TreeNode {
 
 ## JavaScript 
 
+> 递归法：
+
 ```javascript
 /**
  * Definition for a binary tree node.
@@ -535,6 +537,53 @@ var mergeTrees = function (root1, root2) {
     return preOrder(root1, root2);
 };
 ```
+> 迭代法：
+
+```javascript
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root1
+ * @param {TreeNode} root2
+ * @return {TreeNode}
+ */
+var mergeTrees = function(root1, root2) {
+    if (root1 === null) return root2;
+    if (root2 === null) return root1;
+
+    let queue = [];
+    queue.push(root1);
+    queue.push(root2);
+    while (queue.length) {
+        let node1 = queue.shift();
+        let node2 = queue.shift();;
+        node1.val += node2.val;
+        if (node1.left !== null && node2.left !== null) {
+            queue.push(node1.left);
+            queue.push(node2.left);
+        }
+        if (node1.right !== null && node2.right !== null) {
+            queue.push(node1.right);
+            queue.push(node2.right);
+        }
+        if (node1.left === null && node2.left !== null) {
+            node1.left = node2.left;
+        }
+        if (node1.right === null && node2.right !== null) {
+            node1.right = node2.right;
+        } 
+    }
+    return root1;
+};
+
+```
 
 
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