Submission #134419

#TimeUsernameProblemLanguageResultExecution timeMemory
134419dualityTents (JOI18_tents)C++11
100 / 100
240 ms71032 KiB
#define DEBUG 0 #include <bits/stdc++.h> using namespace std; #if DEBUG // basic debugging macros int __i__,__j__; #define printLine(l) for(__i__=0;__i__<l;__i__++){cout<<"-";}cout<<endl #define printLine2(l,c) for(__i__=0;__i__<l;__i__++){cout<<c;}cout<<endl #define printVar(n) cout<<#n<<": "<<n<<endl #define printArr(a,l) cout<<#a<<": ";for(__i__=0;__i__<l;__i__++){cout<<a[__i__]<<" ";}cout<<endl #define print2dArr(a,r,c) cout<<#a<<":\n";for(__i__=0;__i__<r;__i__++){for(__j__=0;__j__<c;__j__++){cout<<a[__i__][__j__]<<" ";}cout<<endl;} #define print2dArr2(a,r,c,l) cout<<#a<<":\n";for(__i__=0;__i__<r;__i__++){for(__j__=0;__j__<c;__j__++){cout<<setw(l)<<setfill(' ')<<a[__i__][__j__]<<" ";}cout<<endl;} // advanced debugging class // debug 1,2,'A',"test"; class _Debug { public: template<typename T> _Debug& operator,(T val) { cout << val << endl; return *this; } }; #define debug _Debug(), #else #define printLine(l) #define printLine2(l,c) #define printVar(n) #define printArr(a,l) #define print2dArr(a,r,c) #define print2dArr2(a,r,c,l) #define debug #endif // define #define MAX_VAL 999999999 #define MAX_VAL_2 999999999999999999LL #define EPS 1e-6 #define mp make_pair #define pb push_back // typedef typedef unsigned int UI; typedef long long int LLI; typedef unsigned long long int ULLI; typedef unsigned short int US; typedef pair<int,int> pii; typedef pair<LLI,LLI> plli; typedef vector<int> vi; typedef vector<LLI> vlli; typedef vector<pii> vpii; typedef vector<plli> vplli; // ---------- END OF TEMPLATE ---------- #define MOD 1000000007 LLI inv(LLI n) { int e = MOD-2; LLI r = 1; while (e > 0) { if (e & 1) r *= n,r %= MOD; e >>= 1; n *= n,n %= MOD; } return r; } LLI fact[3001],invf[3001],invpow2[6001]; LLI dp[3001][3001]; LLI choose(LLI n,LLI k) { return (fact[n]*((invf[k]*invf[n-k]) % MOD)) % MOD; } int main() { int H,W; cin >> H >> W; int i,j; LLI ans = 0; fact[0] = invf[0] = 1; for (i = 1; i <= max(H,W); i++) fact[i] = (fact[i-1]*i) % MOD,invf[i] = inv(fact[i]); invpow2[0] = 1; for (i = 1; i <= H+W; i++) invpow2[i] = (invpow2[i-1]*inv(2)) % MOD; for (i = 0; i <= W; i++) dp[0][i] = 1; for (i = 1; i <= H; i++) { dp[i][0] = 1; for (j = 1; j <= W; j++) dp[i][j] = (dp[i-1][j]+4*j*dp[i-1][j-1]) % MOD; } for (i = 0; i <= H; i++) { for (j = 0; j <= W; j++) { if ((i+2*j <= H) && (j+2*i <= W)) { LLI x = (((choose(H,i)*choose(W,2*i)) % MOD)*fact[2*i]) % MOD; LLI y = (((choose(W-2*i,j)*choose(H-i,2*j)) % MOD)*fact[2*j]) % MOD; ans += ((x*y) % MOD)*((dp[H-i-2*j][W-j-2*i]*invpow2[i+j]) % MOD); ans %= MOD; } } } cout << (ans+MOD-1) % MOD << endl; return 0; }
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