Basic C++ Algorithms: Sorting, Searching, and Generating

Standard STL Algorithms

Instead of writing your own loops, C++ offers optimized algorithms in the <algorithm> and <numeric> headers. Here are four key categories:

1. Sorting

The most common function is std::sort, which operates in $O(N \log N)$ time.

cpp

std::vector<int> v = {5, 2, 8, 1, 9};
std::sort(v.begin(), v.end()); // Sorts in ascending order

2. Searching

std::find: Searches for an element in any container (linear complexity).
std::binary_search: Very fast searching in sorted data.

cpp

auto it = std::find(v.begin(), v.end(), 8);
if (it != v.end()) { /* Found! */ }

3. Copying

std::copy allows moving data from one location to another. Often used with std::back_inserter.

cpp

std::vector<int> v2;
std::copy(v.begin(), v.end(), std::back_inserter(v2));

4. Sequence Generation and Filling

std::fill: Fills a range with a single value.
std::iota: (from <numeric> header) Generates a sequence of increasing numbers (e.g., 1, 2, 3...).

cpp

std::vector<int> data(10);
std::iota(data.begin(), data.end(), 1); // Fills from 1 to 10

Best Practice: Prefer algorithms over manual for loops. They are better optimized by the compiler and less prone to off-by-one errors.

Standard STL Algorithms

Instead of writing your own loops, C++ offers optimized algorithms in the <algorithm> and <numeric> headers. Here are four key categories:

1. Sorting

The most common function is std::sort, which operates in

O(N \log N)

time.

cpp

std::vector<int> v = {5, 2, 8, 1, 9};
std::sort(v.begin(), v.end()); // Sorts in ascending order

2. Searching

std::find: Searches for an element in any container (linear complexity).

std::binary_search: Very fast searching in sorted data.

cpp

auto it = std::find(v.begin(), v.end(), 8);
if (it != v.end()) { /* Found! */ }

3. Copying

std::copy allows moving data from one location to another. Often used with std::back_inserter.

cpp

std::vector<int> v2;
std::copy(v.begin(), v.end(), std::back_inserter(v2));

4. Sequence Generation and Filling

std::fill: Fills a range with a single value.

std::iota: (from <numeric> header) Generates a sequence of increasing numbers (e.g., 1, 2, 3...).

cpp

std::vector<int> data(10);
std::iota(data.begin(), data.end(), 1); // Fills from 1 to 10

Best Practice: Prefer algorithms over manual for loops. They are better optimized by the compiler and less prone to off-by-one errors.

Basic C++ Algorithms: Sorting, Searching, and Generating

Standard STL Algorithms

1. Sorting

2. Searching

3. Copying

4. Sequence Generation and Filling

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Basic C++ Algorithms: Sorting, Searching, and Generating

Standard STL Algorithms

1. Sorting

2. Searching

3. Copying

4. Sequence Generation and Filling

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