2 files changed, 51 insertions, 0 deletions
diff --git a/works/solutions/cpp/897.cpp b/works/solutions/cpp/897.cpp
new file mode 100644
index 0000000..720847b
--- /dev/null
+++ b/works/solutions/cpp/897.cpp
@@ -0,0 +1,37 @@
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
+ * };
+ */
+class Solution {
+public:
+    std::vector<TreeNode*> result;
+
+    void InOrderTraverse(TreeNode* root) {
+        if (root->left != nullptr)
+            InOrderTraverse(root->left);
+        result.push_back(root);
+        if (root->right != nullptr)
+            InOrderTraverse(root->right);
+    }
+
+    TreeNode* increasingBST(TreeNode* root) {
+        InOrderTraverse(root);
+
+        const auto end = result.end();
+        auto iter1 = result.begin();
+        auto iter2 = result.begin() + 1;
+        for (; iter2 != end; ++iter1, ++iter2) {
+            const auto node = *iter1;
+            node->left = NULL;
+            node->right = *iter2;
+        }
+        (*iter1)->left = (*iter1)->right = NULL;
+
+        return result.front();
+    }
+};
diff --git a/works/solutions/cpp/96.cpp b/works/solutions/cpp/96.cpp
new file mode 100644
index 0000000..a67a59a
--- /dev/null
+++ b/works/solutions/cpp/96.cpp
@@ -0,0 +1,14 @@
+class Solution {
+public:
+    // catalan number:
+    // f(n) = f(0) * f(n-1) + f(1) * f(n-2) + ... + f(n-1)*f(0)
+    // f(n) = 2(2n-1) * f(n-1) / (n+1)
+    // f(n) = C(2n, n) / (n+1)
+    int numTrees(int n) {
+        long long result = 1;
+        for (int i = 2; i <= n; i++) {
+            result = 2 * (2 * i - 1) * result / (i + 1);
+        }
+        return result;
+    }
+};