add cpp solution

jinshendan · jinshendan · commit 928a0dbde20f · 2020-05-24T10:21:03.000+02:00
diff --git a/May-LeetCoding-Challenge/24-Construct-Binary-Search-Tree-From-Preorder-Traversal/Construct-Binary-Search-Tree-From-Preorder-Traversal.cpp b/May-LeetCoding-Challenge/24-Construct-Binary-Search-Tree-From-Preorder-Traversal/Construct-Binary-Search-Tree-From-Preorder-Traversal.cpp
@@ -0,0 +1,16 @@
+class Solution {
+public:
+    TreeNode* construct(int i, int j, vector<int>& preorder){
+        if (i > j) return NULL;
+        TreeNode* root = new TreeNode(preorder[i]);
+        int k = i;
+        while (k <= j and preorder[k] <= preorder[i]) k++;
+        root->left = construct(i+1, k-1, preorder);
+        root->right = construct(k, j, preorder);
+        return root;
+    }
+    
+    TreeNode* bstFromPreorder(vector<int>& preorder) {
+        return construct(0, preorder.size() - 1, preorder);
+    }
+};
