Create binary-tree-longest-consecutive-sequence.cpp

Author: kamyu104

C++/binary-tree-longest-consecutive-sequence.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:
+    int longestConsecutive(TreeNode* root) {
+        int max_len = 0;
+        longestConsecutiveHelper(root, &max_len);
+        return max_len;
+    }
+
+    int longestConsecutiveHelper(TreeNode *root, int *max_len) {
+        if (!root) {
+            return 0;
+        }
+
+        const int left_len = longestConsecutiveHelper(root->left, max_len);
+        const int right_len = longestConsecutiveHelper(root->right, max_len);
+
+        int cur_len = 1;
+        if (root->left && root->left->val == root->val + 1) {
+            cur_len = max(cur_len, left_len + 1);
+        }
+        if (root->right && root->right->val == root->val + 1) {
+            cur_len = max(cur_len, right_len + 1);
+        }
+        *max_len = max(*max_len, max(cur_len, max(left_len, right_len)));
+        return cur_len;
+    }
+};