Create univalued-binary-tree.cpp

Author: kamyu104

C++/univalued-binary-tree.cpp

@@ -0,0 +1,40 @@
+// 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:
+    bool isUnivalTree(TreeNode* root) {
+        vector<TreeNode*> s{root};
+        while (!s.empty()) {
+            auto node = s.back(); s.pop_back();
+            if (!node) {
+                continue;
+            }
+            if (node->val != root->val) {
+                return false;
+            }
+            s.emplace_back(node->left);
+            s.emplace_back(node->right);
+        }
+        return true;
+    }
+};
+
+// Time:  O(n)
+// Space: O(h)
+class Solution2 {
+public:
+    bool isUnivalTree(TreeNode* root) {
+        return (!root->left || (root->left->val == root->val & isUnivalTree(root->left))) &&
+               (!root->right || (root->right->val == root->val & isUnivalTree(root->right)));
+    }
+};