Submission #246272

#TimeUsernameProblemLanguageResultExecution timeMemory
246272kostia244Ruins 3 (JOI20_ruins3)C++17
58 / 100
26 ms512 KiB
#include<bits/stdc++.h> using namespace std; using ll = long long; const int maxn = 66, mod = 1e9 + 7; int n, h[maxn][maxn][2], dp[maxn][maxn], a[maxn], pa[maxn], fact[maxn], inv[maxn]; inline void add(int &a, int b) { a = a+b > mod ? a+b-mod : a+b; } inline int mul(int a, int b) { return a*1ll*b%mod; } int bp(int a, int p) { int r = 1; while(p) { if(p&1) r = mul(a, r); a = mul(a, a), p>>=1; } return r; } void setup() { for(int i = 0; i < maxn; i++) if(i < 2) fact[i] = inv[i] = 1; else fact[i] = i, inv[i] = mod - mul(mod/i, inv[mod%i]); for(int* a : {fact, inv}) for(int i = 2; i < maxn; i++) a[i] = mul(a[i-1], a[i]); } inline int nck(int n, int k) { return n < 0 || k > n ? 0 : mul(fact[n], mul(inv[n-k], inv[k])); } inline int A(int n, int k) { return n < 0 || k > n ? 0 : mul(fact[n], inv[n-k]); } void calch() { h[0][0][0] = 1; for(int i = 0; i < n; i++) for(int j = i; j <= n; j++) { for(int f = 0; f < 2; f++) { add(h[i+1][j][f], mul(h[i][j][f], inv[2])); add(h[i+1][j+1][f], h[i][j][f]); add(h[i+1][j+2][f], mul(h[i][j][f], inv[2])); } add(h[i+1][j][1], mul(h[i][j][0], inv[2])); add(h[i+1][j+1][1], mul(h[i][j][0], inv[2])); } } inline int prod(int l, int r) { if(r < l) return 1; if(l <= 0) return 0; return mul(fact[r], inv[l-1]); } inline int contrib(int lst, int i) { int N = lst - (i>1?pa[i-2]:0); return prod(N-a[i-1]+1, N); } void calcdp() { dp[0][0] = 1; for(int i = 0; i < n; i++) for(int lst = 0; lst <= i; lst++) { //if(dp[i][lst]) cout << i << " " << lst << " " << dp[i][lst] << " IS BEING PROCESSED\n"; if(!dp[i][lst]) continue; int t = 1, q, v; for(int ni = i+1; ni <= n; ni++) { for(int nlst = lst+1; nlst <= n; nlst++) { int dif = nlst-lst-1; q = mul(t, contrib(nlst, ni)); //cout << q << '\n'; q = mul(q, mul(h[dif][dif][0] + h[dif][dif][1], A(ni-lst-1, dif))); //cout << dif << " " << h[dif][dif][0] << " / " << h[dif][dif][1] << " / " << A(ni-lst-1, dif) << " " << ni-lst-1 << " " << dif << '\n'; //cout << ni << " " << nlst << " += " << q << '\n'; add(dp[ni][nlst], mul(q, dp[i][lst])); } //cout << ni << " dsalkjfslak " << contrib(lst, ni) << '\n'; t = mul(t, contrib(lst, ni)); if(t == 0) break; } } } int main() { cin.tie(0)->sync_with_stdio(0); setup(); cin >> n; for(int i = 0; i < n; i++) cin >> a[i]; reverse(a, a+n); if(a[0] != 2*n) return cout << 0, 0; for(int i = 0; i < n; i++) a[i] = a[i] - a[i+1] - 1; pa[0] = a[0]; for(int i = 1; i < n; i++) pa[i] = pa[i-1] + a[i]; calch(); calcdp(); //cout << h[1][1][0] << " / " << h[1][1][1] << '\n'; //cout << h[1][2][0] << " / " << h[1][2][1] << '\n'; //cout << h[2][2][0] << " / " << h[2][2][1] << " " << contrib(3, 3) << '\n'; //cout << h[2][3][0] << " / " << h[2][3][1] << '\n'; //cout << h[2][4][0] << " / " << h[2][4][1] << '\n'; cout << dp[n][n] << '\n'; }

Compilation message (stderr)

ruins3.cpp: In function 'void calcdp()':
ruins3.cpp:62:18: warning: unused variable 'v' [-Wunused-variable]
    int t = 1, q, v;
                  ^
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