XOR on Pascal
Topic : Xor + combinatorics + Bigmod
Solution:
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| #include<bits/stdc++.h> | |
| using namespace std; | |
| typedef long long ll; | |
| const ll Max = 100005; | |
| ll MOD = 1000000007; | |
| ll factorial[Max]; | |
| ll BigMod(ll N, ll POW, ll mod) | |
| { | |
| if(POW == 0)return 1; | |
| if(POW&1)return ((N%mod) * BigMod(N, POW - 1, mod)) % mod; | |
| else{ | |
| ll d = BigMod(N, POW/2, mod); | |
| return ((d%mod) * (d%mod)) % mod; | |
| } | |
| } | |
| void fact() | |
| { | |
| factorial[1] = 1; | |
| for(ll i = 2; i < Max; i++){ | |
| factorial[i] = (i*factorial[i-1]) % MOD; | |
| } | |
| } | |
| int main() | |
| { | |
| /* | |
| #ifndef ONLINE_JUDGE | |
| freopen("in.txt", "r", stdin); | |
| freopen("out.txt", "w", stdout); | |
| #endif | |
| */ | |
| //double start_time = clock(); | |
| fact(); | |
| int t; | |
| cin >> t; | |
| while(t--){ | |
| ll n; | |
| cin >> n; | |
| if(n == 0)cout << 1 <<endl; | |
| else if(n&1)cout << 0 << endl; | |
| else{ | |
| ll r = ((factorial[n/2] % MOD) * (factorial[n/2]%MOD) ) %MOD; | |
| cout << (factorial[n] * BigMod(r, MOD-2, MOD) % MOD)<<endl; | |
| } | |
| } | |
| //double end_time = clock(); | |
| //printf( "Time = %lf ms\n", ( (end_time - start_time) / CLOCKS_PER_SEC)*1000); | |
| return 0; | |
| } |
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