Create longest-zigzag-path-in-a-binary-tree.cpp

Author: kamyu104

C++/longest-zigzag-path-in-a-binary-tree.cpp

@@ -0,0 +1,30 @@
+// 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 longestZigZag(TreeNode* root) {
+        int result = 0;
+        dfs(root, &result);
+        return result;
+    }
+
+    pair<int, int> dfs(TreeNode* node, int *result) {
+        if (!node) {
+            return {-1, -1};
+        }
+        const auto& left = dfs(node->left, result);
+        const auto& right = dfs(node->right, result);
+        *result = max({*result, left.second + 1, right.first + 1});
+        return {left.second + 1, right.first + 1};
+    }    
+};