Submission #1195989

#	Time	Username	Problem	Language	Result	Execution time	Memory
1195989		LucaLucaM	Tracks in the Snow (BOI13_tracks)	C++20	19.79 / 100	692 ms	119148 KiB

tracks

#include <iostream>
#include <vector>
#include <algorithm>
#include <cassert>
#include <queue>

using ll = long long;
#define debug(x) #x << " = " << x << '\n'

const int NMAX = 4000;
const int dx[4] = {-1, 0, +1, 0};
const int dy[4] = {0, -1, 0, +1};

char a[NMAX + 2][NMAX + 2];
int dist[NMAX + 2][NMAX + 2];

int main() {
  #ifdef LOCAL
    freopen("input.txt", "r", stdin);
  #endif
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(0);
 
  int n, m;
  std::cin >> n >> m;
  
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      std::cin >> a[i][j];
    }
  }

  int pasite = 0;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      if (a[i][j] != '.') {
        pasite++;
      }
      dist[i][j] = n * m + 1;
    }
  }

  std::deque<std::pair<int, int>> deq;
  
  dist[1][1] = 1;
  deq.push_back({1, 1});

  while (!deq.empty()) {
    auto [x, y] = deq.front();
    deq.pop_front();
    for (int k = 0; k < 4; k++) {
      int xx = x + dx[k];
      int yy = y + dy[k];
      if (xx > 0 && yy > 0 && xx <= n && yy <= m) {
        if (a[x][y] == a[xx][yy] && dist[x][y] < dist[xx][yy]) {
          dist[xx][yy] = dist[x][y];
          deq.push_front({xx, yy});
        } else if (a[x][y] != a[xx][yy] && dist[x][y] + 1 < dist[xx][yy]) {
          dist[xx][yy] = dist[x][y] + 1;
          deq.push_back({xx, yy});
        }
      }
    }
  }
  
  int answer = 0;
  for (int i = 1; i <= n; i++) {
    for (int j = 1; j <= m; j++) {
      answer = std::max(answer, dist[i][j]);
    }
  }
  
  std::cout << answer;
  
  return 0;
}

• Subtask 1: 6.6667 / 30
• Subtask 2: 13.125 / 70