31 lines
1.2 KiB
C++
31 lines
1.2 KiB
C++
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// https://blog.csdn.net/kiwi_berrys/article/details/54834977
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// https://www.cnblogs.com/zjp-shadow/p/7773566.html
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//阶乘逆元
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#define ll long long
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ll fac[1000000 + 5]; //阶乘
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ll inv[1000000 + 5]; //逆元
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void getfac() {
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fac[0] = inv[0] = 1;
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for (int i = 1; i <= 1000000; i++) {
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fac[i] = fac[i - 1] * i % mod;
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inv[i] = quick_power(fac[i], mod - 2);
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//表示i的阶乘的逆元
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}
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}
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//组合数
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inline ll getC(ll n, ll m) // C(n,m) = n!/((n-m)!*m!) % mod
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{
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return fac[n] * inv[n - m] % mod * inv[m] % mod;
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}
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//当 n，m 过大时，可以用Lucas定理降数据
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inline ll Lucas(ll n, ll m) {
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if (n < mod && m < mod) return getC(n, m);
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return Lucas(n / mod, m / mod) * getC(n % mod, m % mod) % mod;
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}
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-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -
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//排列数
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inline ll
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getA(ll n, ll m) // A(n,m) = n!/(n-m)! % mod
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{
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return n * inv[n - m] % mod;
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}
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