TOI7: Sewer

#include <bits/stdc++.h>
using namespace std;

typedef pair<int, int> pii;
typedef tuple<int, int, pii> tiip;

const int N = 100;

char board[N + 10][N + 10];
int row, col;
vector<vector<int>> dist;
queue<tiip> que;

bool isInBoard(int r, int c){
    return r >= 1 && r <= row && c >= 1 && c <= col;
}

bool findCycle(int ur, int uc, int vr, int vc, pii &par){
    if(dist[vr][vc] == -1){
        dist[vr][vc] = dist[ur][uc] + 1;
        que.emplace(vr, vc, pii(ur, uc));
    } else if(pii(vr, vc) != par){
        cout << dist[ur][uc] + 1 << '\n' << vr << ' ' << vc;
        return true;
    }
    return false;
}

int main(){

    scanf("%d%d", &row, &col);
    for(int i = 1; i <= row; ++i){
        for(int j = 1; j <= col; ++j){
            scanf(" %c", &board[i][j]);
        }
    }

    dist.assign(row + 1, vector<int>(col + 1, -1));
    dist[1][1] = 1;
    que.emplace(1, 1, pii(0, 0));
    while(!que.empty()){
        int ur = get<0>(que.front());
        int uc = get<1>(que.front());
        pii par = get<2>(que.front());
        que.pop();
        if(board[ur][uc] == 'D'){ // DOWN
            int vr = ur + 1;
            int vc = uc;
            if(isInBoard(vr, vc) && findCycle(ur, uc, vr, vc, par)){
                return 0;
            }
        } else if(board[ur][uc] == 'R'){ // RIGHT
            int vr = ur;
            int vc = uc + 1;
            if(isInBoard(vr, vc) && findCycle(ur, uc, vr, vc, par)){
                return 0;
            }
        } else if(board[ur][uc] == 'B'){
            // RIGHT
            int vr = ur;
            int vc = uc + 1;
            if(isInBoard(vr, vc) && findCycle(ur, uc, vr, vc, par)){
                return 0;
            }
            // DOWN
            vr = ur + 1;
            vc = uc;
            if(isInBoard(vr, vc) && findCycle(ur, uc, vr, vc, par)){
                return 0;
            }
        }
        // UP
        int vr = ur - 1;
        int vc = uc;
        if(isInBoard(vr, vc) && (board[vr][vc] == 'D' || board[vr][vc] == 'B') && findCycle(ur, uc, vr, vc, par)){
            return 0;
        }
        // LEFT
        vr = ur;
        vc = uc - 1;
        if(isInBoard(vr, vc) && (board[vr][vc] == 'R' || board[vr][vc] == 'B') && findCycle(ur, uc, vr, vc, par)){
            return 0;
        }
    }

    return 0;
}