DATE PROBLEM SOLUTION TOPIC IMPORTANT SEP 1 Count Good Nodes in a Binary Tree LINK Binary Trees SEP 2 Average of Levels in Binary Tree LINK Binary Trees SEP 3 Numbers With Same Consecutive Differences LINK Backtracking SEP 4 Vertical Order Traversal of a Binary Tree LINK Binary Trees SEP 5 N-ary Tree Level Order Traversal Binary Tress SEP 6 Binary Tree Pruning Binary Tree SEP 7 Construct String from Binary Tree Binary Tree SEP 8 Binary Tree Inorder Traversal Binary Tree SEP 9 The Number of Weak Characters in the Game Array SEP 10 Best Time to Buy and Sell Stock IV Dynamic Programming SEP 11 Maximum Performance of a Team Greedy Method SEP 12 Bag of Tokens Greedy Method SEP 13 UTF-8 Validation Bit Manipulation SEP 14 Pseudo-Palindromic Paths in a Binary Tree Binary Tree SEP 15 Find Original Array From Doubled Array Hash Table SEP 16 Maximum Score from Performing Multiplication Operations Dynamic Programming SEP 17 Palindrome Pairs Hash Table SEP 18 Trapping Rain Water Dynamic Programming SEP 19 Find Duplicate File in System Hash Table SEP 20 Maximum Length of Repeated Subarray Dynamic Programming SEP 21 Sum of Even Numbers After Queries Array SEP 22 Reverse Words in a String III String SEP 23 Concatenation of Consecutive Binary Numbers Bit Manipulation SEP 24 Path Sum II BackTracking SEP 25 Design Circular Queue Queue SEP 26 Satisfiability of Equality Equations Graph SEP 27 Push Dominoes Dynamic Programming SEP 28 Remove Nth Node From End of List Linked List SEP 29 Find K Closest Elements Heap SEP 30 The Skyline Problem Divide and Conquer