添加 0538.把二叉搜索树转换为累加树.md C语言

Author: KingArthur0205

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;
+}
+```
+
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