Submission #1087787

#	Time	Username	Problem	Language	Result	Execution time	Memory
1087787		TAhmed33	Skyscraper (JOI16_skyscraper)	C++98	100 / 100	199 ms	122964 KiB

skyscraper

#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize ("Ofast")
typedef long long ll;
const int MOD = 1e9 + 7;
int add (int a, int b) {
	a += b; if (a >= MOD) a -= MOD;
	return a;
}
int sub (int a, int b) {
	a -= b; if (a < 0) a += MOD;
	return a;
}
int mul (int a, int b) {
	return (a * 1ll * b) % MOD;
}
int power (int a, int b) {
	if (!b) return 1;
	int u = power(a, b >> 1);
	u = mul(u, u);
	if (b & 1) u = mul(u, a);
	return u;
}
int n, l, a[101];
const int B = 1000;
int dp[102][102][B + 1][3];
int ans (int x, int y, int z, int c) {
	if (y < 1 || c < 0 || c > 2 || z < 0 || z > B) {
		return 0;
	}
	if (x == n + 1) {
		return y == 1 && z >= 0 && z <= l && c == 0;
	}
	int &ret = dp[x][y][z][c];
	if (ret != -1) {
		return ret;
	}
	ret = 0;
	if (y == 1) {
		ret = add(ret, mul(c, ans(x + 1, y, z + c * a[x], c))); //add to end, and leave open
		ret = add(ret, mul(c, ans(x + 1, y, z + c * a[x], c - 1))); //add to end, and close
		ret = add(ret, mul(c, ans(x + 1, y + 1, z + c * a[x], c))); //add new open component 
		ret = add(ret, mul(c, ans(x + 1, y + 1, z + c * a[x], c - 1))); //add new closed component
	} else {
		int u = 2 * y - 2 + c;
		ret = add(ret, mul(c, ans(x + 1, y + 1, z + u * a[x], c))); //add new open component to end
		ret = add(ret, mul(c, ans(x + 1, y + 1, z + u * a[x], c - 1))); //add new closed component to end 
		ret = add(ret, mul(c, ans(x + 1, y, z + u * a[x], c - 1))); //add to end and close
		ret = add(ret, mul(y - 1, ans(x + 1, y + 1, z + u * a[x], c))); //insert new component in the middle
		ret = add(ret, mul(y - 1, ans(x + 1, y - 1, z + u * a[x], c))); //merge two components
		ret = add(ret, mul(u, ans(x + 1, y, z + u * a[x], c))); //add to end of any component
	}
	return ret;
}
void solve () {
	memset(dp, -1, sizeof(dp));
	cin >> n >> l;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	if (n == 1) {
		cout << 1 << '\n';
		return;
	}
	sort(a + 1, a + n + 1);
	for (int i = n; i >= 1; i--) {
		a[i] = a[i] - a[i - 1];
	}
	a[1] = 0;
	int sum = ans(2, 1, 0, 1);
	sum = mul(sum, 2);
	sum = add(sum, ans(2, 1, 0, 2));
	cout << sum << '\n';
}				
signed main () {
	ios::sync_with_stdio(0); cin.tie(0);
	int tc = 1; //cin >> tc;
	while (tc--) solve();
}

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