Merge branch 'youngyangyang04:master' into master

Author: learnerInTheFirstStage

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

problems/0977.有序数组的平方.md

@@ -100,6 +100,18 @@ public:
 ## 其他语言版本
 
 ### Java：
+排序法
+```Java
+class Solution {
+    public int[] sortedSquares(int[] nums) {
+        for (int i = 0; i < nums.length; i++) {
+            nums[i] = nums[i] * nums[i];
+        }
+        Arrays.sort(nums);
+        return nums;
+    }
+}
+```
 
 ```Java
 class Solution {