BOJ 15683: 감시

작성일

https://www.acmicpc.net/problem/15683

  • 2월동안 187문제 풀기(지난달 누적 87개) (18/187)
  • 빠르고 침착하게 완전탐색
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#include <bits/stdc++.h>
using namespace std;

int N, M, cnt, ans = 100;
struct Point { int x, y, type; };
vector<vector<int>> arr;
vector<Point> cctv;

void input() {
  cin >> N >> M;
  arr.resize(N, vector<int>(M));
  for(int i = 0; i < N; i++) {
    for(int j = 0; j < M; j++) {
       cin >> arr[i][j];
       if(arr[i][j] == 0) cnt++;
       else if(arr[i][j] < 6) cctv.push_back({i,j,arr[i][j]});
    }
  }
}

const int dx[4] = {-1,0,1,0};
const int dy[4] = {0,1,0,-1};
bool bound(int x, int y) {
  return x >= 0 && x < N && y >= 0 && y < M;
}

void fill(int x, int y, int d) {
  while(1) {
    int nx = x + dx[d];
    int ny = y + dy[d];
    if (!bound(nx,ny)) break;
    if(arr[nx][ny] == 6) return;
    if(arr[nx][ny] == 0) arr[nx][ny] = 7, cnt--;
    x = nx, y = ny;
  }
}

void go(int cc) {
  if(cc == cctv.size()) {
    ans = min(ans, cnt);
    return;
  }

  auto bak = arr;
  int bakCnt = cnt;
  Point cur = cctv[cc];
  for(int d = 0; d < 4; d++) {
    fill(cur.x, cur.y, (d+0)%4);
    if(cur.type == 2 || cur.type == 4 || cur.type == 5)
      fill(cur.x, cur.y, (d+2)%4);
    if(cur.type == 3 || cur.type == 4 || cur.type == 5)
      fill(cur.x, cur.y, (d+1)%4);
    if(cur.type == 5)
      fill(cur.x, cur.y, (d+3)%4);
    go(cc+1);
    arr = bak;
    cnt = bakCnt;
  }
}

int main() {
  input();
  go(0);
  cout << ans;
}