class Solution { public: int diameterOfBinaryTree(TreeNode* root) { auto _ = solve(root); return ans; } int solve(TreeNode *root) { if(root == nullptr) return 0; int lefLen = solve(root -> left); int rigLen = solve(root -> right); ans = max(ans, lefLen + rigLen); return max(lefLen, rigLen) + 1; } int ans = 0; }; ...