Submission #261893

#	Time	Username	Problem	Language	Result	Execution time	Memory
261893		Saboon	Boat (APIO16_boat)	C++14	9 / 100	751 ms	5624 KiB

boat

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int maxn = 500 + 10;
const int mod = 1e9 + 7;

int a[maxn], b[maxn];
int dp[maxn][2*maxn], pd[2*maxn][maxn], c[maxn][maxn];
int revpw[maxn];

int power(int a, int b){
	if (b == 0)
		return 1;
	int ret = power(a,b/2);
	ret = 1LL*ret*ret%mod;
	if (b & 1)
		ret = 1LL*ret*a%mod;
	return ret;
}

int main(){
	ios_base::sync_with_stdio(false);
	int n;
	cin >> n;
	vector<int> cmp;
	for (int i = 1; i <= n; i++){
		cin >> a[i] >> b[i];
		b[i] ++;
		cmp.push_back(a[i]);
		cmp.push_back(b[i]);
	}
	sort(cmp.begin(), cmp.end());
	cmp.resize(unique(cmp.begin(),cmp.end())-cmp.begin());
	for (int i = 1; i <= n; i++){
		a[i] = lower_bound(cmp.begin(),cmp.end(),a[i]) - cmp.begin() + 1;
		b[i] = lower_bound(cmp.begin(),cmp.end(),b[i]) - cmp.begin() + 1;
	}
	c[0][0] = 1;
	for (int N = 1; N <= n; N++){
		c[N][0] = 1;
		for (int R = 1; R <= N; R++)
			c[N][R] = (c[N][R-1]+c[N-1][R-1]) % mod;
	}
	for (int i = 1; i <= 500; i++)
		revpw[i] = power(i, mod-2);

	for (int i = 1; i < cmp.size(); i++){
		int m = cmp[i]-cmp[i-1];
		pd[i][1] = m;
		int Cmk = m;
		for (int j = 2; j <= min(n,m); j++){
			for (int k = 2; k <= j; k++){
				Cmk = 1LL*Cmk*revpw[k]%mod*(m-k+1)%mod;
				pd[i][j] = (pd[i][j] + 1LL*c[j-2][k-2]*Cmk) % mod;
			}
		}
	}
	dp[0][0] = 1;
	for (int i = 0; i < cmp.size(); i++)
		dp[0][i] = 1;
	for (int i = 1; i <= n; i++){
		for (int j = a[i]; j < b[i]; j++){
			int cnt = cmp[j]-cmp[j-1];
			for (int k = i-1; k >= 0; k--){
				dp[i][j] = (dp[i][j] + 1LL*pd[j][i-k]*dp[k][j-1]) % mod;
				if (a[k] > j or b[k] <= j)
					break;
			}
		}
		for (int j = a[i]; j < cmp.size(); j++)
			dp[i][j] = (dp[i][j] + dp[i][j-1]) % mod;
		for (int j = 0; j < cmp.size(); j++)
			dp[i][j] = (dp[i][j] + dp[i-1][j]) % mod;
	}
	cout << (dp[n][cmp.size()-1]+mod-1) % mod << endl;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:47:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 1; i < cmp.size(); i++){
                  ~~^~~~~~~~~~~~
boat.cpp:59:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < cmp.size(); i++)
                  ~~^~~~~~~~~~~~
boat.cpp:63:8: warning: unused variable 'cnt' [-Wunused-variable]
    int cnt = cmp[j]-cmp[j-1];
        ^~~
boat.cpp:70:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = a[i]; j < cmp.size(); j++)
                      ~~^~~~~~~~~~~~
boat.cpp:72:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0; j < cmp.size(); j++)
                   ~~^~~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 0 / 22
• Subtask 3: 0 / 27
• Subtask 4: 0 / 42