백준 17142번 연구소 3 C++

출처 : https://www.acmicpc.net/problem/17142

 

활성화되는 바이러스의 모든 경우에 대하여 bfs를 해서 가장 작은 시간을 찾았다.

 

#include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <algorithm>
#include <utility>
#include <stack>
#include <queue>
#include <math.h>
#include <set>
#include <map>
#include <list>
#include <unordered_map>
#include <unordered_set>
#include <iomanip>
#include <limits.h>

using namespace std;
using int64 = long long;

const int MAX = 987654321;

int n, m;
int targetCnt;
int ans = MAX;

int dRow[4] = { -1,0,1,0 };
int dCol[4] = { 0,1,0,-1 };

struct Info {
    int row;
    int col;
    int moveCnt;
};

vector<vector<int>> board;
vector<pair<int, int>> viruses;
vector<int> idxes;
vector<bool> bt_found;
vector<vector<bool>> found;

void Bfs() {
    int cnt = viruses.size();
    found = vector<vector<bool>>(n, vector<bool>(n, false));
    queue<Info> q;
    int moveCnt = 0;
    for (int i = 0; i < idxes.size(); i++) {
        int idx = idxes[i];
        int row = viruses[idx].first;
        int col = viruses[idx].second;
        q.push({ row,col,0 });
        found[row][col] = true;
    }
    while (!q.empty()) {
        auto curr = q.front();
        q.pop();
        if (board[curr.row][curr.col] != 2)
            cnt++;
        moveCnt = curr.moveCnt;
        if (cnt == targetCnt)
            break;
        for (int i = 0; i < 4; i++) {
            int nextRow = curr.row + dRow[i];
            int nextCol = curr.col + dCol[i];
            if (nextRow < 0 || nextRow >= n) continue;
            if (nextCol < 0 || nextCol >= n) continue;
            if (board[nextRow][nextCol] == 1) continue;
            if (found[nextRow][nextCol]) continue;
            q.push({ nextRow,nextCol,curr.moveCnt + 1 });
            found[nextRow][nextCol] = true;
        }
    }
    if (cnt == targetCnt) {
        ans = min(ans, moveCnt);
    }
}

void BT(int idx) {
    if (idxes.size() >= m) {
        Bfs();
        return;
    }
    for (int i = idx; i < viruses.size(); i++) {
        if (bt_found[i]) continue;
        bt_found[i] = true;
        idxes.push_back(i);
        BT(i + 1);
        bt_found[i] = false;
        idxes.pop_back();
    }
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n >> m;
    targetCnt = n * n;
    board = vector<vector<int>>(n, vector<int>(n));
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < n; j++) {
            cin >> board[i][j];
            if (board[i][j] == 1)
                targetCnt--;
            else if (board[i][j] == 2) {
                viruses.push_back({ i,j });
            }
                
        }
    }
    bt_found = vector<bool>(viruses.size(), false);
    BT(0);
    if (ans == MAX) {
        ans = -1;
    }
    cout << ans;
}