CSES_ProblemSet_2021/Labyrinth.cpp at main · Prix2010/CSES_ProblemSet_2021 · GitHub

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#include <bits/stdc++.h>
using namespace std;
int i_B,j_B;
int n,m;
char ans[1001][1001];
int please = 1;

void BFS(int i_A,int j_A,vector<vector<char>>&array,vector<vector<bool>>&check){
    queue<pair<int,int>>current;
    current.push(make_pair(i_A,j_A));

    while(current.size()){
        int curr_i = current.front().first;
        int curr_j = current.front().second;
        current.pop();
        // cout << curr_i << " " << curr_j << endl;

        if(curr_i == i_B && curr_j == j_B){return;}

        if((curr_i + 1 < n && array[curr_i+1][curr_j] != '#') && !check[curr_i + 1][curr_j]){
            ans[curr_i+1][curr_j] = 'D';
            current.push(make_pair(curr_i+1,curr_j));
            check[curr_i+1][curr_j] =true;
            }
        if((curr_i - 1 >= 0 && array[curr_i-1][curr_j] != '#' )&& !check[curr_i-1][curr_j]){
            ans[curr_i-1][curr_j] = 'U';
            current.push(make_pair(curr_i-1,curr_j));
            check[curr_i-1][curr_j] =true;
            }
        if((curr_j + 1 < m && array[curr_i][curr_j+1] != '#' )&& !check[curr_i][curr_j+1]){
            ans[curr_i][curr_j+1] = 'R';
            current.push(make_pair(curr_i,curr_j+1));
            check[curr_i][curr_j+1] =true;
            }
        if((curr_j - 1 >= 0 && array[curr_i][curr_j-1] != '#' )&& !check[curr_i][curr_j-1]){
            ans[curr_i][curr_j-1] = 'L';
            current.push(make_pair(curr_i,curr_j-1));
            check[curr_i][curr_j-1] =true;
            }
    }

    please = 0;

}


int main(){
    cin >> n >> m;

    vector<vector<char>>maze(n);
    vector<vector<bool>>check(n);
    int i_A,j_A;


    for(int i = 0  ; i < n ; i ++){
        for(int j = 0 ;  j < m ; j ++){
            char x;
            cin >>x;
            if(x == 'A'){
                i_A = i;
                j_A = j;
            }else if(x == 'B'){
                i_B = i;
                j_B = j;
            }
            maze[i].push_back(x);
            check[i].push_back(false);
        }
    }

    BFS(i_A,j_A,maze,check);
    if(!please){cout << "NO";return 0;}
    cout << "YES" << endl;
    vector<char>final_ans;

    while(!(i_B == i_A && j_B == j_A)){
        final_ans.push_back(ans[i_B][j_B]);
        if(ans[i_B][j_B] == 'U'){i_B++;}
        else if(ans[i_B][j_B] == 'D'){i_B--;}
        else if(ans[i_B][j_B] == 'L'){j_B++;}
        else if(ans[i_B][j_B] == 'R'){j_B--;}
    }

    cout << final_ans.size() << endl;
    for(auto a = final_ans.rbegin(); a != final_ans.rend();a++)cout << *a;
    cout << endl;

    return 0;
}