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Submission #246272

# Submission time Handle Problem Language Result Execution time Memory
246272 2020-07-08T13:52:07 Z kostia244 Ruins 3 (JOI20_ruins3) C++17
58 / 100
 26 ms 512 KB 
#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

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

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 384 KB Output is correct
2 Correct 5 ms 384 KB Output is correct
3 Correct 5 ms 384 KB Output is correct
4 Correct 5 ms 384 KB Output is correct
5 Correct 5 ms 384 KB Output is correct
6 Correct 5 ms 384 KB Output is correct
7 Correct 5 ms 384 KB Output is correct
8 Correct 5 ms 384 KB Output is correct
9 Correct 5 ms 384 KB Output is correct
10 Correct 4 ms 384 KB Output is correct

Subtask #2
52.0 / 52.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 384 KB Output is correct
2 Correct 5 ms 384 KB Output is correct
3 Correct 5 ms 384 KB Output is correct
4 Correct 5 ms 384 KB Output is correct
5 Correct 5 ms 384 KB Output is correct
6 Correct 5 ms 384 KB Output is correct
7 Correct 5 ms 384 KB Output is correct
8 Correct 5 ms 384 KB Output is correct
9 Correct 5 ms 384 KB Output is correct
10 Correct 4 ms 384 KB Output is correct
11 Correct 6 ms 384 KB Output is correct
12 Correct 5 ms 384 KB Output is correct
13 Correct 7 ms 384 KB Output is correct
14 Correct 5 ms 256 KB Output is correct
15 Correct 4 ms 384 KB Output is correct
16 Correct 5 ms 384 KB Output is correct
17 Correct 5 ms 436 KB Output is correct
18 Correct 26 ms 384 KB Output is correct
19 Correct 22 ms 384 KB Output is correct
20 Correct 21 ms 384 KB Output is correct

Subtask #3
0 / 42.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 384 KB Output is correct
2 Correct 5 ms 384 KB Output is correct
3 Correct 5 ms 384 KB Output is correct
4 Correct 5 ms 384 KB Output is correct
5 Correct 5 ms 384 KB Output is correct
6 Correct 5 ms 384 KB Output is correct
7 Correct 5 ms 384 KB Output is correct
8 Correct 5 ms 384 KB Output is correct
9 Correct 5 ms 384 KB Output is correct
10 Correct 4 ms 384 KB Output is correct
11 Correct 6 ms 384 KB Output is correct
12 Correct 5 ms 384 KB Output is correct
13 Correct 7 ms 384 KB Output is correct
14 Correct 5 ms 256 KB Output is correct
15 Correct 4 ms 384 KB Output is correct
16 Correct 5 ms 384 KB Output is correct
17 Correct 5 ms 436 KB Output is correct
18 Correct 26 ms 384 KB Output is correct
19 Correct 22 ms 384 KB Output is correct
20 Correct 21 ms 384 KB Output is correct
21 Runtime error 6 ms 512 KB Execution killed with signal 11 (could be triggered by violating memory limits)
22 Halted 0 ms 0 KB -