Today I have done leetcode's February LeetCoding Challenge with cpp.

February LeetCoding Challenge 27

Description

Diameter of Binary Tree

Given the root of a binary tree, return the length of the diameter of the tree.

The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.

The length of a path between two nodes is represented by the number of edges between them.

Example 1:

Input: root = [1,2,3,4,5]
Output: 3
Explanation: 3 is the length of the path [4,2,1,3] or [5,2,1,3].

Example 2:

Input: root = [1,2]
Output: 1

Constraints:

• The number of nodes in the tree is in the range [1, 104].
• -100 <= Node.val <= 100

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
  int answer;
  int pathLength(TreeNode * root) {
    if(!root) return 0;
    int left = pathLength(root->left);
    int right = pathLength(root->right);
    answer = max(answer, left + right);
    return 1 + max(left, right);
  }
public:
  int diameterOfBinaryTree(TreeNode* root) {
    pathLength(root);
    return answer;
  }
};

// Accepted
// 105/105 cases passed (3 ms)
// Your runtime beats 95.23 % of cpp submissions
// Your memory usage beats 70.17 % of cpp submissions (19 MB)