摘要：
强连通分量 一个结论: 在有向图中, 一个联通块能被所有点遍历当且仅当图中只有一个连通块出度为零 cpp include include include include include include include using namespace std; const int MAXN = 100 阅读全文
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FFT https://www.luogu.org/problemnew/solution/P3723 重点在于构造卷积的形式 cpp include include include include include include using namespace std; const int MAX 阅读全文
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FFT $$E_i = F_i / q_i = \sum_{i j} \frac{q _ j} {(i j)^2}$$ 设 $p _ i = q_{n i}$ $g(i) = \frac 1 {i^2}$ 则 $E_i = \sum_{j=1}^{i 1} q _ i g(j i) \sum _ { 阅读全文