GCC 13.2.0 (C++20 Standard)Isolated Sandbox

Online C++ Compiler — Write & Run C++ Online

Veyrai's Online C++ Compiler is powered by GCC 13.2.0 under the modern C++20 standard. It provides native support for Standard Template Library (STL) containers (vector, unordered_map, priority_queue), smart pointers (unique_ptr, shared_ptr), lambdas, and fast standard I/O for competitive programming and systems engineering interviews.

Example:

Execution Output

Click "Run (Ctrl+Enter)" to compile and execute your C++ program in the isolated sandbox.

How to Use the Online C++ Compiler

Modern C++20 Standard

Write modern C++ with auto type inference, range-based for loops, structured bindings, and STL algorithms out of the box.

Fast Standard Input & Output

Use std::cin and std::cout. For high-volume competitive programming inputs, include 'std::ios_base::sync_with_stdio(false); std::cin.tie(NULL);'.

Full STL Included

Include headers like <vector>, <string>, <unordered_map>, <algorithm>, and <memory>. All headers compile with high-level optimization flags.

Prepare for High-Frequency Trading & Systems Roles

After testing your C++ algorithms, practice answering tough questions on memory layout, move semantics, and cache locality in Veyrai AI interviews.

C++ Code Examples & Algorithms

Each example is verified to run in our production GCC 13.2.0 (C++20 Standard) runtime. Click "Load in Editor" to test and modify any example above.

1. Standard Input with cin & cout

Parse space-separated words and numbers from stdin using stream operators.

Time: O(1)

#include <iostream>
#include <string>

int main() {
    std::string topic;
    int number;

    std::cout << "Reading topic and number from stdin...\n";
    if (std::cin >> topic >> number) {
        std::cout << "Topic parsed: " << topic << std::endl;
        std::cout << "Value parsed: " << number << std::endl;
        std::cout << "Squared:      " << (number * number) << std::endl;
    } else {
        std::cout << "Please provide inputs in the stdin drawer.\n";
    }
    return 0;
}

2. Vector Sorting & Binary Search with STL

Utilize std::vector and std::lower_bound for fast binary searching over numeric data.

Time: O(N log N)

#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    std::vector<int> numbers = { 45, 12, 85, 32, 89, 39, 69, 44, 42 };

    // Sort in ascending order
    std::sort(numbers.begin(), numbers.end());

    std::cout << "Sorted vector: ";
    for (int n : numbers) std::cout << n << " ";
    std::cout << std::endl;

    int target = 44;
    auto it = std::lower_bound(numbers.begin(), numbers.end(), target);

    if (it != numbers.end() && *it == target) {
        std::cout << "Found target " << target << " at index: " 
                  << std::distance(numbers.begin(), it) << std::endl;
    } else {
        std::cout << "Target " << target << " not found." << std::endl;
    }

    return 0;
}

3. Frequency Counter with std::unordered_map

Count character frequencies in linear time with O(1) average lookup using hash tables.

Time: O(N)

#include <iostream>
#include <string>
#include <unordered_map>

int main() {
    std::string text = "veyrai artificial intelligence interview platform";
    std::unordered_map<char, int> freq;

    for (char c : text) {
        if (c != ' ') {
            freq[c]++;
        }
    }

    std::cout << "Character Frequencies for: \"" << text << "\"\n";
    for (const auto& [ch, count] : freq) {
        if (count > 2) {
            std::cout << "  '" << ch << "' appeared " << count << " times\n";
        }
    }

    return 0;
}

Common C++ Beginner Mistakes & Fixes

Off-by-One Array Indexing & Segmentation Fault

Accessing 'vec[vec.size()]' accesses out-of-bounds memory. In release builds, 'operator[]' does not perform bounds checking.

Fix: Use 'vec.at(index)' during development for bounds-checked access, or verify 'index < vec.size()'.

Iterator Invalidation

Inserting or deleting elements from containers like std::vector can trigger reallocation, making existing pointers and iterators dangling.

Fix: Capture returned iterators from erase() or push_back(), e.g. 'it = vec.erase(it);'.

Forgetting Virtual Destructor in Base Classes

Deleting a derived class object through a pointer to a base class without a virtual destructor causes undefined behavior and resource leaks.

Fix: Always declare virtual destructors: 'virtual ~Base() = default;' in polymorphic base classes.

Environment Specifications

Language: C++
Compiler / Engine: GCC 13.2.0 (C++20 Standard)
Standard Input: Supported (stdin)
Isolation Layer: Dockerized Sandbox
Execution Timeout: 8s to 25s max
Guest Access: Allowed (Rate limited)

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