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37 lines
839 B
C++
37 lines
839 B
C++
#define _CRT_SECURE_NO_WARNINGS
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#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
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#include <bits/stdc++.h>
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using namespace std;
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const int N = 2e5 + 50;
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using ll = long long;
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ll fac[N];
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ll mod = 1e9 + 7;
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ll qpow(ll a, ll b)
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{
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ll ans = 1;
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for (; b; b >>= 1, a = a * a % mod)
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if (b & 1)
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ans = ans * a % mod;
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return ans;
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}
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ll inv(ll x) { return qpow(x, mod - 2); }
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ll C(ll n, ll m)
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{
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if (m > n || m < 0) return 0;
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return fac[n] * inv(fac[n - m] * fac[m] % mod) % mod;
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}
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int main()
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{
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fac[0] = 1;
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for (int i = 1; i < N; i++) fac[i] = fac[i - 1] * i % mod;
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int T;
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cin >> T;
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while (T--)
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{
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long long m, n;
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cin >> m >> n;
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cout << ((C(n + m, m) - (C(n + m - 1, m - 1) * 2) % mod + mod) % mod) << endl;
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}
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return 0;
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}
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