Submission

PPPPPPP

Score: 100

User: Monasm

Problemset: Sirabyrinth 1

Language: cpp

Time: 0.002 second

Submitted On: 2024-11-16 21:19:56

#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>
#include <functional>
#include <queue>
#include <stack>

#define debug(...) Debug(#__VA_ARGS__, __VA_ARGS__)
using namespace std;

template<typename T>
typename std::enable_if<std::is_integral<T>::value>::type
Debug(const char* name, T value) {
    std::cout << name << " : " << value << '\n';
}

template<typename T, typename... Args>
typename std::enable_if<std::is_integral<T>::value>::type
Debug(const char* names, T value, Args... args) {
    const char* comma = strchr(names, ',');
    std::cout.write(names, comma - names) << " : " << value << " | ";
    Debug(comma + 1, args...);
}

vector<pair<int, int>> dir = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};
const string S = "URDL";
const int inf = 1e9;

void solve(){
    int n, m, a, b; cin >> n >> m;
    vector<string> grid(n);
    vector<vector<int>> dist(n, vector<int>(m, inf));
    for (int i = 0;i < n;i++){
        cin >> grid[i];
        for (int j = 0;j < m;j++)
            if (grid[i][j] == 'S') 
                a = i, b = j;
    }
    struct A{
        int i, j, w;
    };

    auto invalid = [&](int i, int j) -> bool {
        return i < 0 || i >= n || j < 0 || j >= m || grid[i][j] == '#';
    };

    queue<A> q;
    q.push({a, b, 0});
    while (!q.empty()){
        auto [i, j, w] = q.front(); q.pop();
        if (dist[i][j] != inf) continue;
        dist[i][j] = w;
        if (i == 0 || i == n-1 || j == 0 || j == m-1){
            stack<char> ans;
            int ni = i, nj = j;

            while (ni != a || nj != b){
                for (int x = 0;x < 4;x++){
                    int di = dir[x].first, dj = dir[x].second;
                    if (invalid(ni-di, nj-dj)) continue;
                    if (dist[ni][nj] == dist[ni-di][nj-dj] + 1){
                        ans.push(S[x]);
                        ni -= di, nj -= dj;
                        break;
                    }
                }
            }
            cout<<ans.size()<<endl;
            while (!ans.empty()){
                cout << ans.top();
                ans.pop();
            }
            return ;
        }
        for (auto [di, dj]:dir){
            if (invalid(i+di, j+dj)) continue;
            q.push({i+di, j+dj, w+1});
        }
    }

}

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0);
    int q = 1; //cin >> q;
    while (q--){
        solve();
    }
}