leetcode 3174 Clear Digits stack

3192 Minimum Operations to Make Binary Array Elements Equal to One II - find alternating binary num

3191 Minimum Operations to Make Binary Array Elements Equal to One I - sliding window with varying

973 K Closest Points to Origin heap

1367 Linked List in Binary Tree - recursion

3275 K th Nearest Obstacle Queries - heap

3279 Maximum Total Area Occupied by Pistons track transition times and direction changes

3228 Maximum Number of Operations to Move Ones to the End sum of partial sums

1945 Sum of Digits of String After Convert

leetcode 1110 Delete Nodes And Return Forest - good example of recursion

leetcode 3174 Clear Digits stack

leetcode 881 Boats to Save People - two-pointer

leetcode 129 Sum Root to Leaf Numbers traversal

leetcode 3106 Lexicographically Smallest String After Operations With Constraint greedy linear ti

leetcode 442 Find All Duplicates in an Array - use index to indicate appearance

leetcode 1669 Merge In Between Linked Lists - work with list or linked list

leetcode 452 Minimum Number of Arrows to Burst Balloons - interval merge type

leetcode 238 Product of Array Except Self - partial product

leetcode 876 Middle of the Linked List - fast slow pointers

leetcode 791 Custom Sort String - custom sorting key

leetcode 349 Intersection of Two Arrays - two-pointer trick

leetcode 141 Linked List Cycle - fast-slow-pointers

leetcode 543 [Facebook, Apple, Bloomberg, Google Interview Q] Diameter of Binary Tree - Recursion

leetcode 1043 Partition Array for Maximum Sum - DP

leetcode 1247 Minimum Swaps to Make Strings Equal - count and distribute