ICPC 2018 Yokohama Regional Problem C

C.cpp

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct Seat {
  int x;
  int y;
};

int distance(int r, int s, const Seat& seat) {
  const int dx = (seat.x <= s) ? (s - seat.x + 1) : (seat.x - s);
  const int dy = r - seat.y;
  return dx + dy;
}

int solve(int r, int s, int p, const vector<Seat>& seats) {
  vector<int> dist(p);
  for (int i = 0; i < p; ++i) {
    dist[i] = distance(r, s, seats[i]);
  }
  sort(dist.begin(), dist.end(), greater<int>());
  int max_time = 0;
  for (int i = 0; i < p; ++i) {
    max_time = max(max_time, dist[i] + (i + 1));
  }
  return max_time;
}

int main() {
  int r, s, p;
  cin >> r >> s >> p;
  vector<Seat> seats(p);
  for (int i = 0; i < p; ++i) {
    cin >> seats[i].y >> seats[i].x;
  }
  std::cout << solve(r, s, p, seats) << std::endl;
  return 0;
}