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Data Structures and Algorithms in C

Q: What should I know before learning data structures in C?

Pointers, structs, arrays, and malloc and free. Pointers most of all: a linked list is a chain of struct node *next fields, and a binary tree is two of them per node. If pointers still feel shaky, Coddy's C course covers them first, free.

C gives you arrays, structs and pointers, and nothing else, so every structure on this path is one you build: a stack from an array, a linked list from malloc, a hash table from buckets of nodes. It is the classic university course, taken hands-on, followed by sorting, recursion, graphs and graded interview problems. Free, in your browser, with a certificate on most courses.

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377 lessons228 challenges702 quiz questions

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Data structures in C, step by step

38 courses377 lessons228 challenges702 quiz questions

Each step is a set of existing Coddy courses, and every Start button opens them in C. The three courses not taught in C yet are listed after the steps.

1
Step 1
Data Structures Series, part one
Start this stepStartStack, queue, binary tree, hash table and linked list, each built from scratch in C with structs, pointers and malloc, then used to solve problems. The five structures behind most interview questions, with every byte accounted for.Start
5 courses, in order
66 lessons34 challenges
2
Step 2
Data Structures Series, part two
Start this stepStartDoubly linked list, heaps and priority queues, tries, graphs and the self-balancing AVL tree. In C a trie is an array of child pointers per node and a graph an array of adjacency lists, so this is the step that makes pointers second nature.Start
5 courses, in order
72 lessons42 challenges
3
Step 3
Sorting algorithms
Start this stepStartBubble, selection, insertion, merge, quick, heap, counting and radix sort, written in C and watched in the visualizer. The standard library's one sort, qsort, takes a comparison function pointer; after this step you can write both the comparator and the sort behind it.Start
8 courses, in order
74 lessons31 challenges319 questions
4
Step 4
Recursive thinkingDedicated page
Start this stepStartRecursion challenges in C. Dynamic programming (taught in Python) and bit manipulation (taught in C++) are listed after the steps, and the second is closer than it sounds: C++ kept C's bitwise operators exactly as they are.Start Dedicated page15 lessons15 challenges
5
Step 5
Graph algorithms
Start this stepStartBreadth-first and depth-first search, Dijkstra, Bellman-Ford, topological sort, Kruskal and Prim in C, on the graph you built in step two. C has no priority queue, so the heap you wrote in step two is the one Dijkstra needs.Start
7 courses, in order
63 lessons21 challenges383 questions
6
Step 6
Interview practice
Start this stepStartTen interview challenge packs and two coding-problem banks, all twelve in C and graded by test cases: unfamiliar problems, solved without a tutorial. The Python interview series, Python only, is listed after the steps.Start
12 courses, in order
87 lessons85 challenges

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Why learn data structures in C on Coddy

Nothing is hidden. C's standard library has no list, map or queue, so there is no built-in to lean on: every node is a struct, every link a pointer, every allocation a malloc you free. Structures learned this way are the ones you understand in every other language afterwards.
The university course, done hands-on. Data structures in C is a core course in many computer science degrees. This path covers the same ground, stack to AVL tree, the sorts and the graph algorithms, as code you run and get graded on as you write it.
Nearly the whole path in C. Every data structure, sort, graph algorithm, recursion challenge and interview pack is taught in C. The three that are not, dynamic programming and the Python interview series (Python) and bit manipulation (C++, which kept C's bitwise operators), are listed after the steps.
Graded like an interview. Every lesson ends in a C challenge checked by test cases, and when one fails, Bugsy reads your code and nudges you toward the fix without handing over the answer. A free certificate on most courses, each verifiable at its own URL.

Frequently asked questions about data structures in C

Why learn data structures in C?

Because C hides nothing. With no built-in list, map or queue, you implement every structure from blocks of memory and pointers, which is exactly what the structure is. After that, Java's HashMap and Python's dict are the same ideas with the memory management done for you, and you can reason about what they cost.

What should I know before learning data structures in C?

Pointers, structs, arrays, and malloc and free. Pointers most of all: a linked list is a chain of struct node *next fields, and a binary tree is two of them per node. If pointers still feel shaky, Coddy's C course covers them first, free.

How do you implement a hash table in C?

With an array of buckets, a hash function that turns a key into an index, and a rule for two keys that land in the same bucket: usually a linked list per bucket (chaining) or probing for the next free slot. When the table fills past a set load factor, you allocate a bigger array and reinsert everything. The hash table course in step one builds one from scratch.

Is C a good language for coding interviews?

Few candidates interview in C outside embedded and systems roles, because writing a hash table from scratch mid-interview costs time other languages give you for free. The knowledge transfers completely, though, and C++ is a small step away: the same syntax, plus the STL. A common route is to learn the structures in C, then take the interview packs in C++, Java or Python, all of which this path offers.

Which courses on this path are not taught in C?

Three: dynamic programming and the Python interview series are taught in Python, and bit manipulation in C++. They are listed after the steps, each with a link that opens it in its own language. Bit manipulation is the easiest of the three to follow from C: C++ kept C's &, |, ^, ~, << and >> exactly as they are.

Should I learn data structures in C or C++?

C to understand the structures, C++ to use them. In C you build everything, which is why so many degrees teach the subject in it; in C++ you build each structure once and then reach for the STL, which is why competitive programmers use it. Starting in C and moving to C++ loses nothing.

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