diff --git a/problems/0108.将有序数组转换为二叉搜索树.md b/problems/0108.将有序数组转换为二叉搜索树.md
index e82d6e95..213eb2b9 100644
--- a/problems/0108.将有序数组转换为二叉搜索树.md
+++ b/problems/0108.将有序数组转换为二叉搜索树.md
@@ -375,8 +375,25 @@ var sortedArrayToBST = function (nums) {
 };
 ```
 
+## C
+递归
+```c
+struct TreeNode* traversal(int* nums, int left, int right) {
+    if (left > right) 
+        return NULL;
+    int mid = left + ((right - left) / 2);
+    struct TreeNode* root = (struct TreeNode*)malloc(sizeof(struct TreeNode));
+    root->val = nums[mid];
+    root->left = traversal(nums, left, mid - 1);
+    root->right = traversal(nums, mid + 1, right);
+    return root;
+}
 
-
+struct TreeNode* sortedArrayToBST(int* nums, int numsSize) {
+    struct TreeNode* root = traversal(nums, 0, numsSize - 1);
+    return root;
+}
+```
 
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
diff --git a/problems/0538.把二叉搜索树转换为累加树.md b/problems/0538.把二叉搜索树转换为累加树.md
index 6de98c6f..16b00817 100644
--- a/problems/0538.把二叉搜索树转换为累加树.md
+++ b/problems/0538.把二叉搜索树转换为累加树.md
@@ -293,6 +293,27 @@ var convertBST = function (root) {
 };
 ```
 
+##C
+
+递归
+```c
+int pre;
+void traversal(struct TreeNode* node) {
+    if(!node)
+        return ;
+    traversal(node->right);
+    node->val = node->val + pre;
+    pre = node->val;
+    traversal(node->left);
+}
+
+struct TreeNode* convertBST(struct TreeNode* root){
+    pre = 0;
+    traversal(root);
+    return root;
+}
+```
+
 -----------------------
 * 作者微信：[程序员Carl](https://mp.weixin.qq.com/s/b66DFkOp8OOxdZC_xLZxfw)
 * B站视频：[代码随想录](https://space.bilibili.com/525438321)