Merge pull request #2606 from markwang1992/404-sumOfLeftLeaves

404.左叶子之和增加Go递归精简版

problems/0404.左叶子之和.md

@@ -337,6 +337,21 @@ func sumOfLeftLeaves(root *TreeNode) int {
 }
 ```
 
+**递归精简版**
+
+```go
+func sumOfLeftLeaves(root *TreeNode) int {
+    if root == nil {
+        return 0
+    }
+    leftValue := 0
+    if root.Left != nil && root.Left.Left == nil && root.Left.Right == nil {
+        leftValue = root.Left.Val
+    }
+    return leftValue + sumOfLeftLeaves(root.Left) + sumOfLeftLeaves(root.Right)
+}
+```
+
 **迭代法(前序遍历)**
 
 ```go