1008. Construct Binary Search Tree from Preorder Traversal

Author: amitbansal7

construct-binary-search-tree-from-preorder-traversal.cpp

@@ -0,0 +1,24 @@
+// Runtime: 4 ms
+// Memory Usage: 11.1 MB
+class Solution {
+public:
+
+  TreeNode* solve(vector<int>& preorder, int lo, int hi) {
+    if (hi < lo) return NULL;
+
+    TreeNode* root = new TreeNode(preorder[lo]);
+    int mid = lo + 1;
+
+    while (mid < preorder.size() && preorder[mid] < root->val)
+      mid++;
+
+    mid--;
+    root->left = solve(preorder, lo + 1, mid);
+    root->right = solve(preorder, mid + 1, hi);
+    return root;
+  }
+
+  TreeNode* bstFromPreorder(vector<int>& preorder) {
+    return solve(preorder, 0, preorder.size() - 1);
+  }
+};