Uva-11624 (fire)

Uva-11624

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
using namespace std;

const int dx[] = {0, 0, -1, 1};
const int dy[] = {-1, 1, 0, 0};

const int maxn = 1010;

char map[maxn][maxn];
int visit[maxn][maxn];
int times[maxn][maxn];

int row, col;
int Step;


struct node{
    int r, c;
    int step;
    node(int rr, int cc, int ss){
        r = rr;
        c = cc;
        step = ss;
    }
    node(){

    }
};

node Joe, Fire;
queue<node> q;

void clear_queue(){
    while(!q.empty()){
        q.pop();
    }
}

bool legal(int x, int y){
    if(x >= 0 && x < row && y >= 0 && y < col) return true;
    else return false;
}

bool isEscape(int x, int y){
    if(x == 0 || x == row - 1 || y == 0 || y == col - 1) return true;
    else return false;
}

void fireBfs(){
    int i;
    int tx, ty, TIME;
    while(!q.empty()){
        node nd = q.front();
        q.pop();

        for(int i = 0; i < 4; ++i){
            tx = nd.r + dx[i];
            ty = nd.c + dy[i];
            TIME = nd.step + 1;
            if(legal(tx, ty) && (map[tx][ty] == '.' || map[tx][ty] == 'J') && visit[tx][ty] == 0){
                visit[tx][ty] = 1;
                q.push(node(tx, ty, TIME));
                times[tx][ty] = TIME;
            }
        }
    }
}
int joeBfs(){
    int tx, ty, TIME;
    clear_queue();
    q.push(Joe);
    visit[Joe.r][Joe.c] = 1;
    while(!q.empty()){
        node nd = q.front();
        q.pop();

        if(isEscape(nd.r, nd.c)){
            Step = nd.step + 1;
            return 1; 
        } 
        for(int i = 0; i < 4; ++i){
            tx = nd.r + dx[i];
            ty = nd.c + dy[i];
            TIME = nd.step + 1;
            if(legal(tx, ty) && map[tx][ty] == '.' &&visit[tx][ty] == 0 && TIME < times[tx][ty]){
                visit[tx][ty] = 1;
                q.push(node(tx, ty, TIME));
            }
        }
    }
    return 0;   
}


int main(){
    int n;
    scanf("%d", &n);
    while(n--){
        clear_queue();

        scanf("%d%d", &row, &col);
        for(int i = 0; i < row; ++i){
            cin >> map[i];
            for(int j = 0; j < col; ++j){
                if(map[i][j] == 'F'){
                    q.push(node(i, j, 0));
                    times[i][j] = 0;
                    visit[i][j] = 1;
                }
                if(map[i][j] == 'J'){
                    Joe.r = i;
                    Joe.c = j;
                    Joe.step = 0;
                }
            }
        }
        memset(times, 10000, sizeof(times));
        memset(visit, 0, sizeof(visit));
        fireBfs();
        memset(visit, 0, sizeof(visit));
        int flag = joeBfs();
        if(flag) cout << Step <<endl;
        else cout << "IMPOSSIBLE" <<endl;
    }
}