Submission #545377

#	Time	Username	Problem	Language	Result	Execution time	Memory
545377		amunduzbaev	Strange Device (APIO19_strange_device)	C++17	30 / 100	2119 ms	219484 KiB

strange_device

#include "bits/stdc++.h"
using namespace std;

#define ar array
#define i128 __int128
#define int long long

int bp(int a, int b, int mod){
	int r = 1;
	while(b){
		if(b&1){
			r = (i128)r * (i128)a % mod;
		} a = (i128)a * (i128)a % mod, b >>= 1;
	} return r;
}

/*

3 5 12
0 23
60 60
81 83

*/

signed main(){
	ios::sync_with_stdio(0); cin.tie(0);
	
	int n, A, B; cin>>n>>A>>B;
	vector<ar<int, 2>> s(n);
	for(int i=0;i<n;i++){
		cin>>s[i][0]>>s[i][1];
	}
	
	int D = B + 1;
	int G = __gcd(A, D);
	vector<ar<int, 3>> ss;
	vector<ar<int, 2>> a;
	for(int i=0;i<n;i++){
		int l = s[i][0], r = s[i][1];
		int bl = l / B, br = r / B;
		if(bl == br){
			ss.push_back({l % B, r % B, (bl*D) % A / G});
		} else {
			ss.push_back({l % B, B - 1, (bl*D) % A / G});
			ss.push_back({0, r % B, (br*D) % A / G});
			int c = (br - bl - 1);
			if(c){
				a.push_back({((bl+1)*D) % A / G, c});
			}
		}
	}
	
	A /= G, D /= G;
	int res = 0;
	if(A == 1 && !a.empty()){
		cout<<B<<"\n";
		return 0;
	}
	
	vector<ar<int, 2>> tot;
	i128 inv = 1;
	if(!a.empty()){
		inv = bp(D, A - 2, A);
		for(auto& x : a){
			x[0] = (i128)x[0] * inv % A;
			if(x[1] >= A){
				cout<<A * B<<"\n";
				return 0;
			}
			x[1] = (x[0] + x[1] - 1) % A;
			if(x[0] <= x[1]) tot.push_back({x[0], x[1]});
			else {
				tot.push_back({x[0], A - 1});
				tot.push_back({0, x[1]});
			}
		}
		
		sort(tot.begin(), tot.end());
		int r = -1;
		for(auto& x : tot){
			if(r < x[0]){
				res += (x[1] - x[0] + 1) * B;
				r = x[1];
			} else if(r < x[1]){
				res += (x[1] - r) * B;
				r = x[1];
			} x[1] = r;
		}
	}
	
	sort(ss.begin(), ss.end());
	map<int, int> mm;
	for(auto& x : ss){
		if(!a.empty()){
			int p = (i128)x[2] * inv % A;
			auto it = lower_bound(tot.begin(), tot.end(), (ar<int, 2>){p + 1, -1});
			if(it != tot.begin()){
				it--;
				if(p <= (*it)[1]) continue;
			}
		}
		
		if(!mm.count(x[2]) || mm[x[2]] < x[0]) res += (x[1] - x[0] + 1), mm[x[2]] = x[1];
		else if(mm[x[2]] < x[1]) res += (x[1] - mm[x[2]]), mm[x[2]] = x[1];
	}
	
	cout<<res<<"\n";
}

• Subtask 1: 0 / 10
• Subtask 2: 5 / 5
• Subtask 3: 0 / 5
• Subtask 4: 5 / 5
• Subtask 5: 0 / 5
• Subtask 6: 0 / 20
• Subtask 7: 20 / 20
• Subtask 8: 0 / 30