Create flip-binary-tree-to-match-preorder-traversal.cpp

Author: kamyu104

C++/flip-binary-tree-to-match-preorder-traversal.cpp

@@ -0,0 +1,39 @@
+// Time:  O(n)
+// Space: O(h)
+
+/**
+ * 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:
+    vector<int> flipMatchVoyage(TreeNode* root, vector<int>& voyage) {
+        vector<int> result;
+        int i = 0;
+        return dfs(root, voyage, &i, &result) ? result : vector<int>{-1};
+    }
+
+private:
+     bool dfs(const TreeNode* root, vector<int>& voyage,
+              int *i, vector<int> *result) {
+        if (!root) {
+            return true;
+        }
+        if (root->val != voyage[*i]) {
+            return false;
+        }
+        ++(*i);
+        if (root->left && root->left->val != voyage[*i]) {
+            result->emplace_back(root->val);
+            return dfs(root->right, voyage, i, result) &&
+                   dfs(root->left, voyage, i, result);
+        }
+        return dfs(root->left, voyage, i, result) &&
+               dfs(root->right, voyage, i, result);
+     }
+};