Create maximum-binary-tree.cpp

Author: kamyu104

C++/maximum-binary-tree.cpp

@@ -0,0 +1,31 @@
+// Time:  O(n)
+// Space: O(n)
+
+/**
+ * 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:
+    TreeNode* constructMaximumBinaryTree(vector<int>& nums) {
+        // https://github.com/kamyu104/LintCode/blob/master/C++/max-tree.cpp
+        vector<TreeNode *> nodeStack;
+        for (int i = 0; i < nums.size(); ++i) {
+            auto node = new TreeNode(nums[i]);
+            while (!nodeStack.empty() && nums[i] > nodeStack.back()->val) {
+                node->left = nodeStack.back();
+                nodeStack.pop_back();
+            }
+            if (!nodeStack.empty()) {
+                nodeStack.back()->right = node;
+            }
+            nodeStack.emplace_back(node);
+        }
+        return nodeStack.front();
+    }
+};