Yosgi Siqi Liu

Finding the path in a zigzag-labeled binary tree using the symmetry of each level's numbering.

Checking whether a set of ranges fully covers an interval, from brute force to an interval-compression optimization.

Reversing a sublist of a linked list in place using a dummy head and tracking the boundary nodes.

Deep-copying a linked list with random pointers using a hash map from old nodes to new.

Detecting the redundant edge that forms a cycle using a union-find template.

Producing the lexicographically smallest string after swaps by grouping swappable indices with union-find and sorting each group.

Finding the least time to swim across a rising pool by binary-searching the water level and checking reachability with DFS.

Finding the minimum heating radius by locating the nearest heater to each house via binary search.

Finding the minimum banana-eating speed by searching over the range of possible speeds.

Selecting the K points closest to the origin using a heap.