Submission #240517

#	Time	Username	Problem	Language	Result	Execution time	Memory
240517		ruler	Skyscraper (JOI16_skyscraper)	C++14	100 / 100	157 ms	56824 KiB

skyscraper

// IOI 2021
#include <bits/stdc++.h>
using namespace std;

#define endl '\n'
#define ends ' '
#define die(x) return cout << x << endl, 0
#define all(v) v.begin(), v.end()
#define sz(x) (int)(x.size())
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) { cerr << ends << H; debug_out(T...); }
#define debug(...) cerr << "{" << #__VA_ARGS__ << "}:", debug_out(__VA_ARGS__)
typedef long long ll;
typedef pair<int, int> pii;
const int INF = 1e9;
const ll MOD = 1e9 + 7;
 
////////////////////////////////////////////////////////////////////

const int N = 1e2 + 5, L = 1e3 + 5;

int A[N], DP[N][N][L][3];

void Add(int &x, int y) {
	x += y;
	if (x >= MOD) x -= MOD;
}
int SMul(int x, int y) { return 1LL * x * y % MOD; }

int main() {

	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	mt19937 Rnd(time(0));

	int n, l; cin >> n >> l;
	for (int i = 1; i <= n; i++) cin >> A[i];
	if (n == 1) die(1);
	sort(A + 1, A + n + 1);
	DP[1][0][0][1] = 2, DP[1][0][0][2] = 1;
	for (int i = 1; i <= n; i++) for (int j = 0; j <= i; j++) for (int s = 0; s <= l; s++) for (int c = 0; c < 3; c++) {
		int x = A[i + 1] - A[i], y = 2 * j + c, d = s + x * y, p = DP[i][j][s][c];
		if (d >= L || j + c == 0) continue;
		if (j) {
			Add(DP[i + 1][j - 1][d][c], SMul(j, p));
			Add(DP[i + 1][j][d][c], SMul(j << 1, p));
			Add(DP[i + 1][j + 1][d][c], SMul(j, p));
		}
		if (c) {
			Add(DP[i + 1][j][d][c - 1], SMul(c, p));
			Add(DP[i + 1][j][d][c], SMul(c, p));
			Add(DP[i + 1][j + 1][d][c - 1], SMul(c, p));
			Add(DP[i + 1][j + 1][d][c], SMul(c, p));
		}
	}
	int ans = 0;
	for (int i = 0; i <= l; i++) Add(ans, DP[n][0][i][0]);
	cout << ans << endl;

	return 0;
}

• Subtask 1: 5 / 5
• Subtask 2: 15 / 15
• Subtask 3: 80 / 80