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- Someone cool, founder @ coolcompany.com

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JavaBeginner

Filter Invalid Transactions

Use loops and validation checks to clean a list of transactions before further processing.

Challenge: Implement a method that returns transactions where amount > 0 and status is APPROVED.

public static List<Transaction> filterValid(List<Transaction> txs) {
    List<Transaction> result = new ArrayList<>();
    for (Transaction tx : txs) {
        boolean positiveAmount = tx.amount() > 0;
        boolean approved = "APPROVED".equals(tx.status());
        if (positiveAmount && approved) {
            result.add(tx);
        }
    }
    return result;
}

PythonBeginner

Build a Task Prioritizer

Practice list processing and conditionals by sorting tasks based on urgency and due date.

Challenge: Write a function that accepts tasks and returns only the top 3 tasks sorted by priority score.

def score(task):
    urgency = task.get("urgency", 0)
    days_left = task.get("days_left", 7)
    penalty = max(0, 7 - days_left)
    return urgency * 10 + penalty

def top_tasks(tasks):
    ranked = sorted(tasks, key=score, reverse=True)
    top_three = ranked[:3]
    return top_three

JavaBeginner

Filter Invalid Transactions

Use loops and validation checks to clean a list of transactions before further processing.

Challenge: Implement a method that returns transactions where amount > 0 and status is APPROVED.

public static List<Transaction> filterValid(List<Transaction> txs) {
    List<Transaction> result = new ArrayList<>();
    for (Transaction tx : txs) {
        boolean positiveAmount = tx.amount() > 0;
        boolean approved = "APPROVED".equals(tx.status());
        if (positiveAmount && approved) {
            result.add(tx);
        }
    }
    return result;
}

C++Beginner

Track Longest Streak

Strengthen array traversal skills by finding the longest consecutive streak in user activity data.

Challenge: Given a vector of daily activity values, return the length of the longest non-decreasing streak.

int longestStreak(const vector<int>& a) {
    if (a.empty()) return 0;
    int best = 1;
    int cur = 1;
    for (size_t i = 1; i < a.size(); i++) {
        if (a[i] >= a[i - 1]) {
            cur++;
            best = max(best, cur);
        } else {
            cur = 1;
        }
    }
    return best;
}

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PythonBeginner

Build your first coding routine

Start with short daily exercises and simple projects so you build consistent momentum without feeling overwhelmed.

Challenge: Write a function that keeps only unfinished tasks and returns the next 3 tasks to do.

def next_tasks(tasks):
    todo = [t for t in tasks if not t["done"]]
    return todo[:3]

LeetCode Trainer

Practice LeetCode with live AI coaching.

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Guided hints, not full answersTime + space complexity coachingPattern-based question drills