Submission #895478

#	Time	Username	Problem	Language	Result	Execution time	Memory
895478		kevinlu	Tracks in the Snow (BOI13_tracks)	C++14	100 / 100	397 ms	130696 KiB

tracks

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

using ll = long long;

using vi = vector<int>;
#define pb push_back
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()

using pi = pair<int, int>;
#define f first
#define s second
#define mp make_pair

void __print(int x) { cerr << x; }
void __print(long x) { cerr << x; }
void __print(long long x) { cerr << x; }
void __print(unsigned x) { cerr << x; }
void __print(unsigned long x) { cerr << x; }
void __print(unsigned long long x) { cerr << x; }
void __print(float x) { cerr << x; }
void __print(double x) { cerr << x; }
void __print(long double x) { cerr << x; }
void __print(char x) { cerr << '\'' << x << '\''; }
void __print(const char *x) { cerr << '"' << x << '"'; }
void __print(const string &x) { cerr << '"' << x << '"'; }
void __print(bool x) { cerr << (x ? "true" : "false"); }

template <typename T, typename V>
void __print(const pair<T, V> &x) {
  cerr << '{';
  __print(x.first);
  cerr << ',';
  __print(x.second);
  cerr << '}';
}
template <typename T>
void __print(const T &x) {
  int f = 0;
  cerr << '{';
  for (auto &i : x) cerr << (f++ ? "," : ""), __print(i);
  cerr << "}";
}
void _print() { cerr << "]\n"; }
template <typename T, typename... V>
void _print(T t, V... v) {
  __print(t);
  if (sizeof...(v)) cerr << ", ";
  _print(v...);
}
#ifndef ONLINE_JUDGE
#define debug(x...)             \
  cerr << "[" << #x << "] = ["; \
  _print(x)
#else
#define debug(x...)
#endif

void setIO(string s = "") {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  if ((int)s.size()) {
    freopen((s + ".in").c_str(), "r", stdin);
    freopen((s + ".out").c_str(), "w", stdout);
  }
}

int dx[4]{1, -1, 0, 0}, dy[4]{0, 0, 1, -1};

int depth[4000][4000];
string snow[4000];

int main() {
  // 0/1 bfs
  setIO();
  int h, w;
  cin >> h >> w;
  for (int i = 0; i < h; i++) {
    cin >> snow[i];
  }
  deque<pi> dq;
  dq.push_back({0, 0});
  depth[0][0] = 1;
  int ans = 0;
  while (!dq.empty()) {
    pi top = dq.front();
    dq.pop_front();
    ans = max(ans, depth[top.f][top.s]);
    for (int k = 0; k < 4; k++) {
      int nx = top.f + dx[k], ny = top.s + dy[k];
      if (nx < 0 || nx >= h || ny < 0 || ny >= w || depth[nx][ny] != 0 || snow[nx][ny] == '.') {
        continue;
      }
      if (snow[nx][ny] == snow[top.f][top.s]) {
        depth[nx][ny] = depth[top.f][top.s];
        dq.push_front({nx, ny});
      } else {
        depth[nx][ny] = depth[top.f][top.s] + 1;
        dq.push_back({nx, ny});
      }
    }
  }
  cout << ans;
  return 0;
}

Compilation message (stderr)

tracks.cpp: In function 'void setIO(std::string)':
tracks.cpp:64:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   64 |     freopen((s + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
tracks.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen((s + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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