Freestyle linked lists tricks
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A practical walkthrough of linked list techniques in C, starting from a basic stack-style list and progressively enhancing it without changing the core structure. Covers building ordered lists with a double-pointer tail technique, adding O(log n) lookup via an intrusive hash trie (two child pointers per node), and O(1) lookup via a separate MSI hash table index. Also demonstrates multi-map iteration with cursor/iterator patterns. All techniques work without runtime support, making them suitable for embedded systems and WebAssembly.
Questions this post answers
How do I build an ordered linked list in C without dummy nodes or branches?
Use a double-pointer tail technique: initialize a head pointer to null, then keep a pointer-to-pointer (tail) that starts as &head. For each new node, assign it to *tail, then advance tail to &node->next. This appends nodes in order with no branches and works correctly for empty lists too. Systems developers working with custom allocators and data structures find the latest C patterns on daily.dev.
How can I add O(log n) lookup to a C linked list without replacing it?
Add two child pointers to each node to form an intrusive hash trie. When inserting, traverse the trie using successive bits of the 64-bit hash to find an empty slot, then link the node onto the list tail as usual. The result is simultaneously a linked list and a hash map, supporting multi-map iteration without resizing. Developers building low-level data structures without heap overhead track techniques like these on daily.dev.
How do I build a flat hash table index over an existing C linked list for O(1) lookup?
Construct an MSI hash table (slots array sized as a power-of-two) after the list is complete. Walk the list and insert each node pointer into the table using double hashing. Lookup is O(1) and non-intrusive — the list nodes need no extra fields. Multiple tables can index different properties of the same list. Engineers optimizing read-heavy data structures in C or embedded environments find concrete patterns like this on daily.dev.