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Time Complexity · #41 · 2026-05-15

What's the Big-O?

Python ·Difficulty 2/3

How to play

Read the code and pick its time complexity from four Big-O choices. Think about loops, recursion, and hidden costs. Press 1–4 or click to answer.

Directed graph with V vertices and E edges. What is the time complexity?

def topo_sort(graph):
    visited = set()
    stack = []

    def dfs(node):
        visited.add(node)
        for neighbor in graph.get(node, []):
            if neighbor not in visited:
                dfs(neighbor)
        stack.append(node)

    for node in graph:
        if node not in visited:
            dfs(node)
    return stack[::-1]

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Press 1 through 4, or tap a numbered choice, to answer. Back to hub