Ancestor problem :
1.https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/ 2.https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/ 3.https://leetcode.com/problems/maximum-difference-between-node-and-ancestor/ 4.https://leetcode.com/problems/lowest-common-ancestor-of-deepest-leaves/ 5.https://leetcode.com/problems/kth-ancestor-of-a-tree-node/ 6.https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
Root to leaf path problems: 1.https://leetcode.com/problems/binary-tree-paths/ EASY 2.https://leetcode.com/problems/path-sum-iii/submissions/ 3.https://leetcode.com/problems/smallest-string-starting-from-leaf/ 4.https://leetcode.com/problems/sum-of-root-to-leaf-binary-numbers/ 5.https://leetcode.com/problems/insufficient-nodes-in-root-to-leaf-paths/ 6.https://leetcode.com/problems/pseudo-palindromic-paths-in-a-binary-tree/
Serialize and deserialize: 1.https://leetcode.com/problems/serialize-and-deserialize-binary-tree/ Hard 2.https://leetcode.com/problems/verify-preorder-serialization-of-a-binary-tree/ Medium 3.https://leetcode.com/problems/serialize-and-deserialize-bst/ 4.https://leetcode.com/problems/serialize-and-deserialize-bst/
Leaves related problem: 1.https://leetcode.com/problems/sum-of-left-leaves/ EASY 2.https://leetcode.com/problems/leaf-similar-trees/ EASY 3.https://leetcode.com/problems/deepest-leaves-sum/ 4.https://leetcode.com/problems/delete-leaves-with-a-given-value/
Level order traversal: 1.https://leetcode.com/problems/smallest-subtree-with-all-the-deepest-nodes/ 2.https://leetcode.com/problems/path-in-zigzag-labelled-binary-tree/ 3.https://leetcode.com/problems/maximum-level-sum-of-a-binary-tree/ 4.https://leetcode.com/problems/sum-of-nodes-with-even-valued-grandparent/ 5.https://leetcode.com/problems/frog-position-after-t-seconds/ 6.https://leetcode.com/problems/even-odd-tree/ 7.https://leetcode.com/problems/binary-tree-level-order-traversal/ 8.https://leetcode.com/problems/binary-tree-zigzag-level-order-traversal/ 9.https://leetcode.com/problems/binary-tree-level-order-traversal-ii/ 10.https://leetcode.com/problems/binary-tree-right-side-view/ 11.https://leetcode.com/problems/n-ary-tree-level-order-traversal/ 12.https://leetcode.com/problems/find-largest-value-in-each-tree-row/ 13.https://leetcode.com/problems/add-one-row-to-tree/ 14.https://leetcode.com/problems/average-of-levels-in-binary-tree/ 15.https://leetcode.com/problems/maximum-width-of-binary-tree/
Node deletion: 1.https://leetcode.com/problems/delete-nodes-and-return-forest/ 2.https://leetcode.com/problems/delete-node-in-a-bst/
Tree construction: 1.https://leetcode.com/problems/construct-binary-tree-from-preorder-and-postorder-traversal/ 2.https://leetcode.com/problems/all-possible-full-binary-trees/ 3.https://leetcode.com/problems/construct-binary-search-tree-from-preorder-traversal/ 4.https://leetcode.com/problems/recover-a-tree-from-preorder-traversal/ 5.https://leetcode.com/problems/validate-binary-tree-nodes/ 6.https://leetcode.com/problems/number-of-ways-to-reconstruct-a-tree/ 7.https://leetcode.com/problems/merge-bsts-to-create-single-bst/ 8.https://leetcode.com/problems/unique-binary-search-trees-ii/ 9.https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/ 10.https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/ 11.https://leetcode.com/problems/maximum-binary-tree 12.https://leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal 13.https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal
Distance between two Nodes: 1.https://leetcode.com/problems/minimum-distance-between-bst-nodes/ 2.https://leetcode.com/problems/sum-of-distances-in-tree/ Hard 3.https://leetcode.com/problems/all-nodes-distance-k-in-binary-tree/
Inorder traversal 1.https://leetcode.com/problems/increasing-order-search-tree/ 2.https://leetcode.com/problems/binary-search-tree-to-greater-sum-tree/ 3.https://leetcode.com/problems/all-elements-in-two-binary-search-trees/ 4.https://leetcode.com/problems/validate-binary-search-tree/ 5.https://leetcode.com/problems/convert-bst-to-greater-tree/
Rangesum of BT 1.https://leetcode.com/problems/range-sum-of-bst/
Flipping: 1.https://leetcode.com/problems/flip-equivalent-binary-trees/ 2.https://leetcode.com/problems/flip-binary-tree-to-match-preorder-traversal/
Check binary tree:- 1.https://leetcode.com/problems/check-completeness-of-a-binary-tree/ 2.https://leetcode.com/problems/check-completeness-of-a-binary-tree/ 3.https://leetcode.com/problems/univalued-binary-tree/
Tree relations: 1.https://leetcode.com/problems/cousins-in-binary-tree/
Counting of nodes: 1.https://leetcode.com/problems/count-good-nodes-in-binary-tree/ 2.https://leetcode.com/problems/number-of-nodes-in-the-sub-tree-with-the-same-label/ 3.https://leetcode.com/problems/number-of-good-leaf-nodes-pairs/ 4.https://leetcode.com/problems/unique-binary-search-trees/
Recovery: 1.https://leetcode.com/problems/recover-binary-search-tree/
Kth smallest : 1.https://leetcode.com/problems/kth-smallest-element-in-a-bst/ 2.https://leetcode.com/problems/kth-largest-element-in-a-stream/
Trimming or pruning: 1.https://leetcode.com/problems/trim-a-binary-search-tree/
Searching: 1.https://leetcode.com/problems/search-in-a-binary-search-tree/
Difference problem in BT: 1.https://leetcode.com/problems/kth-largest-element-in-a-stream/
Tree checking: 1.https://leetcode.com/problems/same-tree/ 2.https://leetcode.com/problems/symmetric-tree/
Depth problem: 1.https://leetcode.com/problems/maximum-depth-of-binary-tree/ 2.https://leetcode.com/problems/minimum-depth-of-binary-tree/ 3.https://leetcode.com/problems/minimum-absolute-difference-in-bst/ 4.https://leetcode.com/problems/maximum-depth-of-n-ary-tree/