[BOJ] 2151. 거울설치 + TC

*거울이 [\] [/] 이 두 방향으로 있다고 생각하고 풀어야 한다. 

처음에는 45도이기 때문에 [/] 만 생각하고 풀었다가 아니라는 것을 알게 됐다. 

 

*처음 [#] 좌표에서 출발해서 4방향 모두 큐에 넣는다. 

*각 방향으로 한 칸 앞으로 전진한 좌표가 거울이면 방향을 바꾸어서 큐에 넣고, 방향을 바꾸지 않는 상태로도 큐에 넣는다. 

이 좌표에 거울을 설치하지 않는 경우도 생각한다. 

 

3

...

*!#

#!!

 

이 예시를 보면 (1, 3)에서 출발해서 (3,1)로 가야하는데 남쪽 방향으로 (3,3)의 거울로 간 후, 방향을 한 번 바꾸면 바로 (3,1)에 접근가능하다. 

 

 

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#include <iostream> #include <vector> #include <queue> #include <cstring> #include <functional> #define INF 987654321 using namespace std;   int n, ans = INF; char map[51][51]; typedef pair<int, int> pp; typedef pair<pp, pp> pppp;   vector<pp> door; int dp[51][51]; bool visited[51][51][4]; int dx[4] = { -1,1,0,0 }, dy[4] = { 0,0,-1,1 };   void bfs() {     priority_queue<pppp, vector<pppp>, greater<pppp>> q;       for (int i = 0; i < 4; i++) {           q.push(pppp(pp(0, i), door[0]));         visited[door[0].first][door[0].second][i] = true;     }       while (!q.empty()) {         int x = q.top().second.first;         int y = q.top().second.second;         int cnt = q.top().first.first;         int dir = q.top().first.second;         q.pop();           //들어온 방향에 따라 반사되는 방향이 달라진다.         if (x == door[1].first && y == door[1].second) {             ans = ans > cnt ? cnt : ans;             continue;         }         //거울은 45도 방향으로 놓여져 있다.         int nx = x + dx[dir];         int ny = y + dy[dir];           if (nx < 0 || nx >= n || ny < 0 || ny >= n || map[nx][ny] == '*' || visited[nx][ny][dir]) continue;             if (map[nx][ny] == '!') {             if (dir <= 1) {                                     q.push({ {cnt + 1, 2},{nx, ny} });                                     q.push({ {cnt + 1, 3},{nx, ny} });             }             else {                                   q.push({ {cnt + 1, 0},{nx, ny} });                                     q.push({ {cnt + 1, 1},{nx, ny} });             }           }         //거울 설치 안하고 그냥 가는 방법도 있음         visited[nx][ny][dir] = true;         q.push({ {cnt, dir}, {nx, ny} });       } } int main() {       ios_base::sync_with_stdio(0);     cin.tie(0);       //양 쪽 문에서 서로가 보여야 하기 때문에 bfs를 두 번 돈다.     cin >> n;         for (int i = 0; i < n; i++) {         for (int j = 0; j < n; j++) {             cin >> map[i][j];               if (map[i][j] == '#') {                 door.push_back({ i, j });             }           }     }     //문을 발견했을 때 나갈수 있는 방향은 모두 나가야 하나?     //아니면 두 문의 상대적인 위치를 알아내서 -> 서로 마주볼 수 있는 방향으로???       bfs();         cout << ans << '\n';         return 0; }

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4 ..#. !..# .*.. !.!. Answer: 3   4 #..! .... .... #... Answer: 0   4 #..! !... .#.. !!.! Answer: 2   5 #!..! **... !!..! .*..* !!..# Answer: 4   4 !!.! #!*# !.!! !*!. Answer: 2   5 ..#.. !.!.! *.*!! ...!* #..!! Answer: 5   4 #..! !!.! *!.* #!.. Answer: 3   5 ***#* *.!!* *.!!* *!!.* *#*** Answer: 4   5 ***#* *!!!* *.*!* *!!** *#*** Answer: 2   3 #.! !!* .!# Answer: 3   7 !!..!.# *.....* .!..!.. !!*.!.! .*!!.*! ...!!.. !*#**** Answer: 5   4 #!!! !!!! !!!! !!!# Answer: 1   4 #!!* *!!! !*!! *!*# Answer: 3   2 #. !# Answer: 1   10 ****#***** !!..!.!..! ......*... ......!..! *!....!..* ......!..! .!....!... ...!*.*... !..!!.!..! ****#***** Answer: 8   50 #!..............................................*! .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .!...............................................! .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .*...........................................!...! .!.......................!...................!...* .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. .................................................. *................................................* !!...............................................# Answer: 8   9 .!*...... ..!.!*!.! #.!*.*.*. !!.*!.!*. .*....... .#......! ......... ......... !.......!   Correct answer: 3   input #1 3 #!. !!. *#.   output #1 1   input #2 3 ... *!# #!!   output #2 1   input #3 2 !# !#   output #3 0   input #4 30 #!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!#   output #4 1     20 #.....!.!........... ******.*.*********** *!....!*.*********** *.****.*.*********** *.**!.!*.*********** *.**.***.*********** *.**!.!*.*********** *.****.*.*********** *.**!.!*.*********** *.**.***.*********** *!..!.......#******* ********.***.******* ********.***.******* ********.***.******* ********.***.******* ********.*!.!******* ********.*.********* ********.*!.!******* ********.***.******* ********!...!*******       ans = 4