22 lines
476 B
C++
22 lines
476 B
C++
constexpr ll MOD = 1e9+7;
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int fact[200002] = { 1 }, ifact[200002] = { 1 };
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int pw(int base, int exp) {
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int res = 1;
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while (exp) {
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if (exp & 1) res = (ll)base * res % MOD;
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exp >>= 1;
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base = (ll)base * base % MOD;
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}
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return res;
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}
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int inv(int x) { return pw(x, MOD - 2); }
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int nCr(int n, int k) { return (ll)fact[n] * ifact[k] % MOD * ifact[n - k] % MOD; }
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for (int i = 0; i < n; ++i) {
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fact[i + 1] = (i + 1ll) * fact[i] % MOD;
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ifact[i + 1] = inv(fact[i + 1]);
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} |