DataslopeC++ Essentials for DSA
A fast refresher on the C++ features used throughout data structures and algorithms
You do not need all of C++ to start solving DSA problems. You need a reliable slice: types, references, const, vectors, functions, templates, lambdas, and a handful of headers.
The compilation model
C++ source files are compiled into object files, then linked with libraries to produce an executable.
Variables, types, and auto
For DSA, use int for ordinary counts, long long for large integer answers, size_t for container sizes, bool for flags, char for characters, and double for floating-point values. auto steps = path.size(); asks the compiler to deduce the type from the initializer.
Signed and unsigned indices
size_t is unsigned. Be careful when counting backward or comparing it with int; many bugs come from values wrapping below zero.
References vs pointers
A reference is another name for an existing object. A pointer stores an address and can be reassigned or be null. Prefer references when a parameter must refer to a valid object; use pointers when null is meaningful.
const and const& parameter passing
Use const when a value should not change. Pass large objects as const& to avoid copying while promising not to modify them.
Headers used throughout this course
| Header | Gives you |
|---|---|
<iostream> | std::cin, std::cout |
<vector> | std::vector |
<string> | std::string |
<algorithm> | sort, min, max, reverse, binary_search |
<unordered_map> | Hash maps |
<queue> | queue, priority_queue |
<stack> | stack |
<numeric> | accumulate, iota, gcd |
A quick tour of std::vector
std::vector is the default sequence container for DSA: fast indexing, compact storage, and amortized O(1) appends. Iterators mark ranges; STL algorithms often use [begin, end).
Function templates
Templates let one function work for many types while still being checked and optimized at compile time.
Lambda expressions
A lambda is an inline function object. Lambdas are used heavily with algorithms such as std::sort.
Practice: functions and templates
Implement int sum(const std::vector<int>& v) so it returns the total of all values in the vector. Do not print inside the function; the provided main will print the result.
Implement a templated function max3<T> that returns the largest of three values. The same function should work for both int and double.
Test your knowledge
When should you prefer a reference parameter like int& x over a pointer parameter like int* x?
When the argument may be missing and represented as null
When the function requires a valid object and may modify it
When you need to allocate memory manually
When you want to store an address in a container
Why pass const std::vector<int>& v instead of std::vector<int> v for a read-only helper function?
It makes the vector sorted automatically
It allows the function to delete elements faster
It avoids copying the whole vector while preventing modification
It converts the vector into an array
Which header provides std::sort?
<iostream>
<vector>
<algorithm>
<queue>
Ready for analysis