https://medium.com/@Sazidz/how-to-detect-cycles-in-a-graph-6236e6eb750

3.cpp

int main() {
    // Input graph here
    
    for (char c : {'A', 'B', 'C'})
        if (status[c] == UNVISITED)
            dfs(c);

    if (hasCycles) {
        // Do something
    }
    
    return 0;
}