Create diameter-of-binary-tree.cpp

Author: kamyu104

C++/diameter-of-binary-tree.cpp

@@ -0,0 +1,31 @@
+// 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 diameterOfBinaryTree(TreeNode* root) {
+        int diameter = 1;
+        depth(root, &diameter);
+        return diameter - 1;
+    }
+
+private:
+    int depth(TreeNode *root, int *diameter) {
+        if (!root) {
+            return 0;
+        }
+        auto left = depth(root->left, diameter);
+        auto right = depth(root->right, diameter);
+        *diameter = max(*diameter, 1 + left + right);
+        return 1 + max(left, right);
+    }
+};