UVA 11624

UVA 11624

• 因为人和火不能模拟出来同时走,
• 那么bfs 火 到个点的时间,
• 然后bfs 人 到个点的时间,判断时间是否满足在火到来之前
• 终点就是越界
• memset(timefire,0x3d,sizeof timefire),我当时设置的是memset(timefire,0,sizeof)就wa了

#include 
#include 
#include 

using namespace std;
const int maxn = 1e3 + 10;
struct node {
    int x,y;
    int step;
    node(){}
    node(int a,int b,int c) {
        x = a; y = b; step = c;
    }
};

int sx,sy;
int n,m;
int next1[4][2] = {0,1,1,0,0,-1,-1,0};
char grid[maxn][maxn];
int timefire[maxn][maxn];
bool vis[maxn][maxn];
queue > qfire;

void bfs_fire(){
    while ( !qfire.empty() ) {
        int x = qfire.front().first;
        int y = qfire.front().second;
        qfire.pop();

        for (int i=0; i<4; i++) {
            int tx = x + next1[i][0];
            int ty = y + next1[i][1];
            if (tx<1 || ty<1 || tx>n || ty>m) continue;
            if (grid[tx][ty] == '#' || vis[tx][ty]) continue;
            
            vis[tx][ty] = 1;
            timefire[tx][ty] = timefire[x][y] + 1;
            qfire.push({tx,ty});
            
        }
    }
}

void bfs() {
	memset(vis,0,sizeof vis);
    queue que;
    vis[sx][sy] = 1;
    que.push( node(sx,sy,0) );

    while ( !que.empty() ) {
        node cur = que.front();
        que.pop();
        
        for(int i=0; i<4; i++) {
            int tx = cur.x + next1[i][0];
            int ty = cur.y + next1[i][1];
            if (tx<1 || ty<1 || tx>n || ty>m) {
				cout << cur.step+1 << endl;
				return ;
			}
            if (grid[tx][ty] == '#' || vis[tx][ty] || cur.step+1 >= timefire[tx][ty]) continue;
            
            vis[tx][ty] = 1;
            que.push( node(tx,ty,cur.step + 1) );
        }
    }
    cout << "IMPOSSIBLE" << endl;
    return ;
}
void init() {
    memset(vis,0,sizeof vis);
    memset(timefire,0x3f,sizeof timefire);
}
int main() {
//	freopen("a.txt","r",stdin);
    int times;
    cin >> times;
    while (times--) {
        init();
        cin >> n >> m;
        for (int i=1; i<=n; i++)
            for (int j=1; j<=m; j++) {
                cin >> grid[i][j];
                if (grid[i][j] == 'J') {
                    sx = i;
                    sy = j;
                }
                else if (grid[i][j] == 'F') {
                    vis[i][j] = 1;
                    timefire[i][j] = 0;
                    qfire.push({i,j});
                }
            }
        bfs_fire();
        bfs();
    }
    return 0;
}