/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

Traversals

Inorder

vector<int> inorderNodes;

void inorderTraversal(TreeNode* node){
    if(node == NULL) return;
    inorderTraversal(node->left);
    inorderNodes.push_back(node->val);
    inorderTraversal(node->right);    
}

BFS

104. Maximum Depth of Binary Tree

199. Binary Tree Right Side View

Binary Search Tree

530. Minimum Absolute Difference in BST