Submission #344197

#	Time	Username	Problem	Language	Result	Execution time	Memory
344197		blue	Strange Device (APIO19_strange_device)	C++11	35 / 100	1864 ms	17212 KiB

strange_device

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
 
/*
Observations:
 
(1, b) = b
 
(b+1, b) = b
 
If a is even,      (a, 1) = a/2
Else if a is odd,  (a, 1) = a
 
b divides (a, b)
 
If b+1 divides a
 
 
If a and b+1 are coprime (a, b) = a*b
 
a*b / gcd(a, b+1) = ;
 
lcm(a, b+1) - a
*/
 
long long long_gcd(long long a, long long b)
{
    // cout << "gcd " << a << ' ' << b << '\n';
    if(a == b) return a;
    if(a < b) swap(a, b);
    if(b == 0) return a;
    return long_gcd(a%b, b);
}
 
long long long_abs(long long x)
{
    if(x >= 0) return x;
    return -x;
}
 
long long long_sign(long long x)
{
    if(x > 0) return 1;
    return -1;
}
 
int main()
{
    int n;
    long long A, B;
    cin >> n >> A >> B;
 
 
 
    long long period = A * B / long_gcd(A, B+1);
 
    // cout << period << '\n';
 
    long long l, r;
 
    if(n == 1)
    {
        cin >> l >> r;
 
 		if(r-l+1 >= period)
        {
            cout << period << '\n';
        }
        else if(l % period <= r % period)
        {
            cout << (r % period) - (l % period) + 1 << '\n';
        }
        else
        {
            cout << period - ((r % period) - (l % period) + 1) + 2 << '\n';
        }
        return 0;
    }
 
    vector<long long> endpoints;
 
    for(int i = 1; i <= n; i++)
    {
        cin >> l >> r;
 
        if(l % period <= r % period)
        {
            endpoints.push_back(l % period + 1);
            endpoints.push_back(-(r % period) - 1 - 1);
        }
        else
        {
            endpoints.push_back(l % period + 1);
            endpoints.push_back(-period - 1);
 
            endpoints.push_back(0 + 1);
            endpoints.push_back(-(r % period) - 1 - 1);
        }
    }
 
 
        // for(long long e: endpoints) cout << e << ' ';
        // cout << '\n';
 
 
    sort(endpoints.begin(), endpoints.end(), [] (long long p, long long q)
    {
        return long_abs(p) < long_abs(q);
    });
 
    // for(long long e: endpoints) cout << e << ' ';
    // cout << '\n';
 
 
    long long res = 0;
 
    long long count = 0;
    count += long_sign(endpoints[0]);
    for(int i = 1; i < endpoints.size(); i++)
    {
        // cout << count << ' ' << long_abs(endpoints[i]) - long_abs(endpoints[i-1]) << '\n';
        if(count > 0) res += long_abs(endpoints[i]) - long_abs(endpoints[i-1]);
        count += long_sign(endpoints[i]);
    }
 
    cout << res << '\n';
}

Compilation message (stderr)

strange_device.cpp: In function 'int main()':
strange_device.cpp:121:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<long long int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  121 |     for(int i = 1; i < endpoints.size(); i++)
      |                    ~~^~~~~~~~~~~~~~~~~~

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