Submission #656449

#	Time	Username	Problem	Language	Result	Execution time	Memory
656449		600Mihnea	Portals (BOI14_portals)	C++17	20 / 100	4 ms	1876 KiB

portals

bool home = 0;
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 1000 + 7;
int n;
int m;
int a[N][N];
int r1;
int c1;
int r2;
int c2;
/// a[i][j] == 1 => (i, j) is a free cell

int dr[] = {-1, 0, 1, 0};
int dc[] = {0, 1, 0, -1};
int d[N][N];

signed main() {
  if (home == 0) {
    ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  } else {
    freopen ("___input___.txt", "r", stdin);
  }
  cin >> n >> m;
  for (int i = 1; i <= n; i++) {
    string s;
    cin >> s;
    assert((int) s.size() == m);
    for (int j = 1; j <= m; j++) {
      char ch = s[j - 1];
      assert(ch == '.' || ch == '#' || ch == 'S' || ch == 'C');
      if (ch != '#') {
        a[i][j] = 1;
      }
      if (ch == 'S') {
        assert(r1 == 0 && c1 == 0);
        r1 = i;
        c1 = j;
      }
      if (ch == 'C') {
        assert(r2 == 0 && c2 == 0);
        r2 = i;
        c2 = j;
      }
      d[i][j] = -1;
    }
  }
  assert(1 <= r1 && r1 <= n);
  assert(1 <= r2 && r2 <= n);
  assert(1 <= c1 && c1 <= m);
  assert(1 <= c2 && c2 <= m);
  queue<pair<int, int>> q;
  q.push({r1, c1});
  d[r1][c1] = 0;

  while (!q.empty()) {
    int r = q.front().first;
    int c = q.front().second;
    q.pop();
    bool some_wall = 0;
    for (int k = 0; k < 4; k++) {
      int rn = r + dr[k];
      int cn = c + dc[k];
      if (a[rn][cn] == 0) {
        some_wall = 1;
      }
      if (a[rn][cn] == 1 && d[rn][cn] == -1) {
        d[rn][cn] = 1 + d[r][c];
        q.push({rn, cn});
      }
    }
    if (some_wall) {
      for (int k = 0; k < 4; k++) {
        int rn = r;
        int cn = c;
        while (a[rn + dr[k]][cn + dc[k]] == 1) {
          rn += dr[k];
          cn += dc[k];
        }
        if (d[rn][cn] == -1) {
          d[rn][cn] = 1 + d[r][c];
          q.push({rn, cn});
        }
      }
    }
  }
  assert(d[r2][c2] != -1);
  cout << d[r2][c2] << "\n";
  return 0;
}
/// :15

Compilation message (stderr)

portals.cpp: In function 'int main()':
portals.cpp:26:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   26 |     freopen ("___input___.txt", "r", stdin);
      |     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 11
• Subtask 2: 0 / 20
• Subtask 3: 20 / 20
• Subtask 4: 0 / 19
• Subtask 5: 0 / 30