Submission #1305659

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Source Code Expand

#include<iostream>
#include<algorithm>
#include<vector>
using namespace std;
long long N, A, B, S[120000], dp[120000][2], mod = 1000000007; vector<long long>EA, EB;
int main() {
	cin >> N >> A >> B; S[1] = -(1LL << 62); S[N + 2] = (1LL << 62); EA.push_back(2); EB.push_back(2);
	for (int i = 2; i <= N + 1; i++) {
		cin >> S[i]; if (S[i] - S[i - 1] < A)EA.push_back(i); if (S[i] - S[i - 1] < B)EB.push_back(i);
	}
	dp[1][0] = 1; dp[1][1] = 1;
	for (int i = 2; i <= N + 1; i++) {
		int pos1 = upper_bound(S, S + N + 3, S[i + 1] - A) - S; pos1--; if (pos1 == i)pos1--;
		int pos2 = upper_bound(EB.begin(), EB.end(), i) - EB.begin(); pos2--; pos2 = EB[pos2] - 1;
		if (pos1 >= pos2)dp[i][0] = (dp[pos1][1] - dp[pos2 - 1][1] + mod) % mod; dp[i][0] += dp[i - 1][0]; dp[i][0] %= mod;
		
		int pos3 = upper_bound(S, S + N + 3, S[i + 1] - B) - S; pos3--; if (pos3 == i)pos3--;
		int pos4 = upper_bound(EA.begin(), EA.end(), i) - EA.begin(); pos4--; pos4 = EA[pos4] - 1;
		if (pos3 >= pos4)dp[i][1] = (dp[pos3][0] - dp[pos4 - 1][0] + mod) % mod; dp[i][1] += dp[i - 1][1]; dp[i][1] %= mod;
	}
	cout << (dp[N + 1][0] + dp[N + 1][1] - dp[N][0] - dp[N][1] + mod * 2) % mod << endl;
	return 0;
}

Submission Info

Judge Result