LA 4324 Ugly Windows (模拟)

https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=2325

　　考细心的模拟，开始的时候，没有注意到不能有其他窗遮盖这个条件，把模拟写成了只要能看到全部窗框就算是满足要求，所以WA了一次。不过很快就找到这个bug了，AC。

　　做法其实很简单，只要沿着边框走一遍就可以了。

代码如下：

#define _clr(x) memset(x, 0, sizeof(x))
#define REP(i, n) for (int i = 0; i < (n); i++)
#define REP_1(i, n) for (int i = 1; i <= (n); i++)

const int dir[4][2] = { {-1, 0}, {1, 0}, {0, -1}, {0, 1}};
bool vis[N][N];
char mat[N][N];

bool test(int x, int y, char ch) {
    _clr(vis);
    int minx = inf, miny = inf, maxx = x, maxy = y;
    int cx = x, cy = y, cnt = 0;
    while (!vis[cx][cy]) {
//        cout << cx << ends << cy << ends << cnt << endl;
        cnt++;
        minx = min(minx, cx), miny = min(miny, cy);
        vis[cx][cy] = true;
        REP(i, 4) {
            int nx = cx + dir[i][0], ny = cy + dir[i][1];
            if (vis[nx][ny] || mat[nx][ny] != ch) continue;
            cx = nx, cy = ny;
            break;
        }
    }
    if (cnt >= 8) {
        REP(d, 4) {
            if (cx + dir[d][0] == x && cy + dir[d][1] == y) {
                INC(i, minx + 1, maxx - 1) {
                    INC(j, miny + 1, maxy - 1) {
                        if (mat[i][j] != '.') return false;
                    }
                }
                return true;
            }
        }
    }
    return false;
}

int mx[30], my[30];

int main() {
//    freopen("in", "r", stdin);
    int n, m;
    while (~scanf("%d%d", &n, &m) && (n + m)) {
        _clr(mat);
        _clr(mx);
        _clr(my);
        REP_1(i, n) {
            scanf("%s", &mat[i][1]);
            REP_1(j, m) {
                if (mat[i][j] != '.') {
//                    cout << i << ends << j << endl;
                    int id = mat[i][j] - 'A';
                    mx[id] = i, my[id] = j;
                }
            }
        }
        REP(i, 26) {
//            cout << mx[i] << ends << my[i] << endl;
            if (mx[i] || my[i]) {
                if (test(mx[i], my[i], i + 'A')) putchar(i + 'A');
            }
        }
        puts("");
    }
    return 0;
}

——written by Lyon