Submission #1235055

#	Time	Username	Problem	Language	Result	Execution time	Memory
1235055		farica	Trains (BOI24_trains)	C++20	58 / 100	211 ms	137440 KiB

Main

#include<bits/stdc++.h>
using namespace std;
using vi = vector<int>;
using pi = pair<int,int>;
typedef long long ll;
#define debug(x) cout << #x << " = " << x << "\n";
#define vdebug(a) cout << #a << " = "; for(auto x: a) cout << x << " "; cout << "\n";
 
const int MOD = 1e9 + 7;
const int INF = 1e9; 
 
template<ll mod>
struct modnum {
	static constexpr bool is_big_mod = mod > numeric_limits<int>::max();
 
	using S = conditional_t<is_big_mod, ll, int>;
	using L = conditional_t<is_big_mod, __int128, ll>;
 
	S x;
 
	modnum() : x(0) {}
	modnum(ll _x) {
		_x %= static_cast<ll>(mod);
		if (_x < 0) { _x += mod; }
		x = _x;
	}
 
	modnum pow(ll n) const {
		modnum res = 1;
		modnum cur = *this;
		while (n > 0) {
			if (n & 1) res *= cur;
			cur *= cur;
						n /= 2;
		}
		return res;
	}
	modnum inv() const { return (*this).pow(mod-2); }
 
	modnum& operator+=(const modnum& a){
		x += a.x;
		if (x >= mod) x -= mod;
		return *this;
	}
	modnum& operator-=(const modnum& a){
		if (x < a.x) x += mod;
		x -= a.x;
		return *this;
	}
	modnum& operator*=(const modnum& a){
		x = static_cast<L>(x) * a.x % mod;
		return *this;
	}
	modnum& operator/=(const modnum& a){ return *this *= a.inv(); }
 
	friend modnum operator+(const modnum& a, const modnum& b){ return modnum(a) += b; }
	friend modnum operator-(const modnum& a, const modnum& b){ return modnum(a) -= b; }
	friend modnum operator*(const modnum& a, const modnum& b){ return modnum(a) *= b; }
	friend modnum operator/(const modnum& a, const modnum& b){ return modnum(a) /= b; }
 
	friend bool operator==(const modnum& a, const modnum& b){ return a.x == b.x; }
	friend bool operator!=(const modnum& a, const modnum& b){ return a.x != b.x; }
	friend bool operator<(const modnum& a, const modnum& b){ return a.x < b.x; }
 
	friend ostream& operator<<(ostream& os, const modnum& a){ os << a.x; return os; }
	friend istream& operator>>(istream& is, modnum& a) { ll x; is >> x; a = modnum(x); return is; }
};
 
using mint = modnum<MOD>;
 
template <class T> class SumSegmentTree {
  private:
	const T DEFAULT = 0;

	vector<T> segtree;
	int len;

  public:
	SumSegmentTree(int len) : len(len), segtree(len * 2, DEFAULT) {}

	void set(int ind, T val) {
		ind += len;
		segtree[ind] = val;
		for (; ind > 1; ind /= 2) {
			segtree[ind / 2] = segtree[ind] + segtree[ind ^ 1];
		}
	}

	T range_sum(int start, int end) {
		T sum = DEFAULT;
		for (start += len, end += len; start < end; start /= 2, end /= 2) {
			if (start % 2 == 1) { sum += segtree[start++]; }
			if (end % 2 == 1) { sum += segtree[--end]; }
		}
		return sum;
	}
};
 
struct DSU{
	vector<int> p, sz, used, mn, mx;
 
	DSU(int n){
		p.assign(n, 0);
		sz.assign(n, 1);
		used.assign(n, 0);
		mx.assign(n, 0);
		mn.assign(n, 0);
 
		for (int i = 0; i < n; i++) p[i] = i;
	}
 
	int find(int u){
		if (p[u] == u) return u;
		p[u] = find(p[u]);
		return p[u];
	}
		void unite(int u, int v){
		u = find(u);
		v = find(v);
		if (u == v) return;
 
		if (sz[u] < sz[v]) swap(u, v);
		p[v] = u;
		sz[u] += sz[v];
		used[u] += used[v];
		mn[u] = min(mn[u], mn[v]);
		mx[u] = max(mx[u], mx[v]);
	}
 
	bool same(int u, int v){
		return find(u) == find(v);
	}
 
	int size(int u){
		u = find(u);
		return sz[u];
	}
};

const int N = 250005;

/*struct BIT {
  ll b[N], n;
  
  void init(int _n) {
	n = _n ;
	for(int i = 0 ; i <= n ; ++i) b[i] = INF;
  }
  inline int lowbit(int x) { return x & (-x); }
  void update(int x, ll v) {
	for(int i = x ; i <= n ; i += lowbit(i)) b[i] = min(v, b[i]);
  }
  ll query(int x) {
	ll ans = INF;
	for(int i = x ; i > 0 ; i -= lowbit(i)) ans = min(ans,b[i]);
	return ans;
  }
} bit[2];*/

int gcd(int a, int b, int& x, int& y) { // x*a + y*b = a1 
    x = 1, y = 0;
    int x1 = 0, y1 = 1, a1 = a, b1 = b;
    while (b1) {
        int q = a1 / b1;
        tie(x, x1) = make_tuple(x1, x - q * x1);
        tie(y, y1) = make_tuple(y1, y - q * y1);
        tie(a1, b1) = make_tuple(b1, a1 - q * b1);
    }
    return a1;
}

int inv_ecd(int a, int m) {
	int x, y;
	int g = gcd(a, m, x, y);
	if(g != 1) return -1;
	x = (x + m) % m;
	return x;
}

const int B = 320;

ll mem[B][B];

void solve() {
	int n;
	cin >> n;	
	vector<ll> d(n), x(n), dp(n, 0);
	dp[0] = 1;
	for(int i=0; i<n; ++i) {
		cin >> d[i] >> x[i];
	}
	/*for(auto it = ma.begin(); it != ma.end(); ++it) {
		vi v = it->second;
		int cur = it->first;
		if(cur > B) {
			for(int a: v) {
				ll R = n-1, rght = a + cur * x[a];
				for(int j=a+cur; j<=min(R,rght); j+=cur) dp[j] = (dp[j] + dp[j-cur]) % MOD;
			}
		} else {
			int cnt = 0;
			vi tmp(cur, 0), rem(n, 0);
			for(int i=0; i<n; ++i) {
				dp[i] = (dp[i] + tmp[i%cur]) % MOD;
				if(cnt != (int)v.size() && v[cnt] == i) {
					tmp[i%cur] = (tmp[i%cur] + dp[i]) % MOD;
					ll R = min((ll)n-1, i + 1ll * x[i] * cur);
					rem[R] = (rem[R] + dp[i]) % MOD;
					++cnt;
				}
				tmp[i%cur] = (tmp[i%cur] - rem[i] + MOD) % MOD;
			}
		}
	}*/
	queue<pair<ll,ll>>Q[n], rem[n];
	for(int i=0; i<n; ++i) {
		for(int j=1; j<B; ++j) dp[i] = (dp[i] + mem[j][i%j]) % MOD;
		ll R = 1ll * x[i] * d[i] + i;
		R = min(R, (ll)n-1);
		if(d[i] >= B) Q[i].push({d[i], R});
		else if(d[i]) {
			mem[d[i]][i%d[i]] = (mem[d[i]][i%d[i]] + dp[i]) % MOD; 
			if(R != n-1) rem[R].push({i, dp[i]}); 
		}
		while(!rem[i].empty()) {
			pair<ll,ll> cur = rem[i].front();
			rem[i].pop();
			int D = d[cur.first];
			mem[D][cur.first%D] = (mem[D][cur.first%D] - cur.second + MOD) % MOD;
		}
		while(!Q[i].empty()) {
			pair<ll,ll> cur = Q[i].front();
			Q[i].pop();
			int nxt = i + cur.first;
			if(nxt > cur.second) continue;
			dp[nxt] = (dp[nxt] + dp[i]) % MOD;
			Q[nxt].push(cur);
		}
	} 
	ll ans = 0;
	for(int i=0; i<n; ++i) {
		ans = (ans + dp[i]) % MOD;
		//cout << i << ": " << dp[i] << endl;
	}
	cout << ans << endl;
}
 
int main(){
	//freopen("N3.in", "r", stdin);
	//freopen("N3.out", "w", stdout);
	ios::sync_with_stdio(0);
	cin.tie(0); cout.tie(0);
	
	int tc=1;
	while (tc--) solve();	
}

• Subtask 1: 8 / 8
• Subtask 2: 0 / 13
• Subtask 3: 16 / 16
• Subtask 4: 34 / 34
• Subtask 5: 0 / 29