33 lines
773 B
C++
33 lines
773 B
C++
#include <bits/stdc++.h>
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using namespace std;
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const int INF = 0x3f3f3f3f;
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typedef long long LL;
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const int N = 1e5 + 10;
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const int mod = 1e9 + 7;
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int fact[N];
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int infact[N];
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int qmi(int a, int k, int p) {
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int res = 1;
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while (k) {
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if (k & 1) res = (LL)res * a % p;
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a = (LL)a * a % p;
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k >>= 1;
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}
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return res;
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}
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int main() {
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fact[0] = infact[0] = 1;
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for (int i = 1; i < N; i++) {
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fact[i] = (LL)fact[i - 1] * i % mod;
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infact[i] = (LL)infact[i - 1] * qmi(i, mod - 2, mod) % mod;
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}
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int n;
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scanf("%d", &n);
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while (n--) {
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int a, b;
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scanf("%d %d", &a, &b);
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printf("%d\n", (LL)fact[a] * infact[b] % mod * infact[a - b] % mod);
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}
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return 0;
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} |