Submission #857901

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Source Code Expand

#ifdef LOCAL111
#else
	#define NDEBUG
#endif
#include <bits/stdc++.h>
const int INF = 1e8;
using namespace std;

#define endl '\n'
#define ALL(a)  (a).begin(),(a).end()
#define SZ(a) int((a).size())
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define RFOR(i,a,b) for (int i=(b)-1;i>=(a);i--)
#define REP(i,n)  FOR(i,0,n)
#define RREP(i,n) for (int i=(n)-1;i>=0;i--)
#define RBP(i,a) for(auto& i : a)
#ifdef LOCAL111
	#define DEBUG(x) cout<<#x<<": "<<(x)<<endl
	template<typename T> void dpite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
#else
	#define DEBUG(x) true
	template<typename T> void dpite(T a, T b){ return; }
#endif
#define F first
#define S second
#define SNP string::npos
#define WRC(hoge) cout << "Case #" << (hoge)+1 << ": "
#define rangej(a,b,c) ((a) <= (c) and (c) < (b))
#define rrangej(b,c) rangej(0,b,c)
template<typename T> void pite(T a, T b){ for(T ite = a; ite != b; ite++) cout << (ite == a ? "" : " ") << *ite; cout << endl;}
template<typename T> bool chmax(T& a, T b){if(a < b){a = b; return true;} return false;}
template<typename T> bool chmin(T& a, T b){if(a > b){a = b; return true;} return false;}

typedef long long int LL;
typedef unsigned long long ULL;
typedef pair<int,int> P;
typedef pair<LL,LL> LP;

void ios_init(){
	//cout.setf(ios::fixed);
	//cout.precision(12);
#ifdef LOCAL111
	return;
#endif
	ios::sync_with_stdio(false); cin.tie(0);	
}

const LL mod = 1e9+7;

int main()
{
	ios_init();
	int n;
	cin >> n;
	vector<LL> p(n);
	vector<int> l(n);
	REP(i,n) cin >> p[i] >> l[i];
	vector<vector<LL>> dp(n);
	{
		dp[0].resize(2*l[0]+1,1);
	}
	FOR(i,1,n){
		LL dis = p[i]-l[i];
		LL pdis = p[i-1]-l[i-1];
		dp[i].resize(2*l[i]+1,0);
		vector<LL> sum(2*l[i-1]+2,0);
		sum[0] = 0;
		REP(j,2*l[i-1]+1) sum[j+1] = (sum[j]+dp[i-1][j])%mod;
		dpite(ALL(sum));
		int po = 0;
		REP(j,2*l[i]+1){
			while(po < 2*l[i-1]+1 and pdis+po < dis+j) po++;
			DEBUG(j); DEBUG(po);
			{
				dp[i][j] = (sum[po]-sum[0]+mod)%mod;
			}
		}
	}
	// REP(i,n) dpite(ALL(dp[i]));
	LL ans = 0;
	RBP(e,dp[n-1]) ans = (ans+e)%mod;
	cout << ans << endl;
	return 0;
}

Submission Info

Judge Result