Best Online Compiler for Competitive Programming and DSA Practice

Whether you're grinding LeetCode, preparing for Codeforces rounds, or mastering Data Structures and Algorithms (DSA), you need fast, reliable code execution that doesn't waste your time with setup.

What Makes a Good Online Compiler for CP?

C++ — The King of Competitive Programming

Our C++ Compiler runs GCC with full STL support:

#include <bits/stdc++.h>
using namespace std;

int main() {
    vector<int> arr = {1, 3, 5, 7, 9, 11, 13};
    int target = 7;

    auto it = lower_bound(arr.begin(), arr.end(), target);
    if (it != arr.end() && *it == target) {
        cout << "Found " << target << " at index " << (it - arr.begin()) << endl;
    }
    return 0;
}

bits/stdc++.h, vector, map, priority_queue, sort — all available.

Python — Algorithm Prototyping

from collections import defaultdict
from heapq import heappush, heappop

def dijkstra(graph, start):
    dist = defaultdict(lambda: float('inf'))
    dist[start] = 0
    heap = [(0, start)]

    while heap:
        d, u = heappop(heap)
        if d > dist[u]:
            continue
        for v, w in graph[u]:
            if dist[u] + w < dist[v]:
                dist[v] = dist[u] + w
                heappush(heap, (dist[v], v))
    return dist

Try it in our Python Compiler.

DSA Topics and Recommended Language

Frequently Asked Questions

Is bits/stdc++.h supported?
Yes. Our C++ compiler runs GCC which includes this competitive programmer's favourite include.

Can I test with custom input?
Yes. Type your test case in the input panel before clicking Run — cin and Scanner read from it.

Does it support Java's Scanner?
Yes. Use Scanner sc = new Scanner(System.in) and provide input in the input field.

Start Practising Now

• C++ Compiler — STL, GCC, fast execution
• Python Compiler — clean syntax, standard library
• Java Compiler — OOP, JDK 21

No account. No installation. No time wasted.