Submission #685211

#	Time	Username	Problem	Language	Result	Execution time	Memory
685211		ToniB	Skyscraper (JOI16_skyscraper)	C++17	100 / 100	119 ms	79460 KiB

skyscraper

#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
const int MAXN = 105;

int n, L, a[MAXN];
long long dp[MAXN][MAXN][1005][3];

int main(){
	cin >> n >> L;
	for(int i = 1; i <= n; ++i) cin >> a[i];
	sort(a + 1, a + n + 1);

	if(n == 1){
		cout << 1; return 0;
	}
	dp[0][0][0][0] = 1;

	for(int i = 1; i <= n; ++i){
		for(int j = 1; j <= i; ++j){
			for(int k = 0; k <= L; ++k){
				for(int m = 0; m < 3; ++m){
					// first i numbers, j components, k is sum, m endpoints filled
					int dif = (a[i + 1] - a[i]) * (2 * j - m);
					if((i != n && m > j) || k < dif) continue;
					// create new component that isnt endpoint
					dp[i][j][k][m] += dp[i - 1][j - 1][k - dif][m];
					
					// create new component that is endpoint
					if(m) dp[i][j][k][m] += dp[i - 1][j - 1][k - dif][m - 1] * (3 - m);
					
					// append on edge of component
					dp[i][j][k][m] += dp[i - 1][j][k - dif][m] * (2 * j - m);
					
					// append end on component
					if(m == 1) dp[i][j][k][m] += dp[i - 1][j][k - dif][m - 1] * 2 * j;
					else if(m == 2){
						if(i < n) dp[i][j][k][m] += dp[i - 1][j][k - dif][m - 1] * (j - 1);
						else dp[i][j][k][m] += dp[i - 1][j][k - dif][m - 1];
					}
					
					// merge two components
					if(i == n){
						dp[i][j][k][m] += dp[i - 1][j + 1][k - dif][m];
					} else {
						dp[i][j][k][m] += dp[i - 1][j + 1][k - dif][m] * (j * (j + 1) - m * j);
					}

					dp[i][j][k][m] %= MOD;
				}
			}
		}
	}
	long long ans = 0;
	for(int i = 0; i <= L; ++i) ans += dp[n][1][i][2];
	cout << ans % MOD;
	return 0;
}

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