Code templates

Here are code templates for common patterns for all the data structures and algorithms looked at in LICC.

Two pointers: one input, opposite ends

Two pointers: two inputs, exhaust both

Sliding window

Build a prefix sum

Efficient string building

In JavaScript, benchmarking shows that concatenation with += is faster than using .join().

Linked list: fast and slow pointer

Reversing a linked list

Find number of subarrays that fit an exact criteria

Monotonic increasing stack

The same logic can be applied to maintain a monotonic queue.

Binary tree: DFS (recursive)

Binary tree: DFS (iterative)

Binary tree: BFS

Graph: DFS (recursive)

For the graph templates, assume the nodes are numbered from 0 to n - 1 and the graph is given as an adjacency list. Depending on the problem, you may need to convert the input into an equivalent adjacency list before using the templates.

Graph: DFS (iterative)

Graph: BFS

Find top k elements with heap

Binary search

Binary search: duplicate elements, left-most insertion point

Binary search: duplicate elements, right-most insertion point

Binary search: for greedy problems

If looking for a minimum:

If looking for a maximum:

Backtracking

Dynamic programming: top-down memoization

Build a trie

Dijkstra's algorithm

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