Submission #988483

#	Time	Username	Problem	Language	Result	Execution time	Memory
988483		kflippy	Tracks in the Snow (BOI13_tracks)	C++17	100 / 100	1087 ms	125020 KiB

tracks

#include <bits/stdc++.h>

using namespace std;

int h, w;
char s[4000][4000];

bool chk(pair<int, int> c)
{
  return c.first > -1 && c.first < h && c.second < w && c.second > -1 && s[c.first][c.second] != '.';
}

int
main()
{
  cin >> h >> w;
  deque<pair<int, int>> q;
  vector<vector<int>> d(h, vector<int>(w));
  d[0][0] = 1;
  for(int i = 0; i < h; ++i) {
    for(int j = 0; j < w; ++j) {
      cin >> s[i][j];
    }
  }
  q.push_front({0, 0});
  vector<int> dx = {-1, 0, 1, 0}, dy = {0, 1, 0, -1};
  int ans = 0;
  while(!q.empty()) {
    pair<int, int> x = q.front();
    q.pop_front();
    ans = max(ans, d[x.first][x.second]);
    for(int i = 0; i < 4; ++i) {
      pair<int, int> y = {x.first + dx[i], x.second + dy[i]};
      if(chk(y) && d[y.first][y.second] == 0) {
        if(s[y.first][y.second] == s[x.first][x.second]) {
          d[y.first][y.second] = d[x.first][x.second];
          q.push_front({y.first, y.second});
        }
        else {
          d[y.first][y.second] = d[x.first][x.second] + 1;
          q.push_back({y.first, y.second});
        }
      }
    }
  }
  cout << ans << "\n";
}

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