HDU 1312 Red and Black 题解

//注意边界判断，调了好久

#include <iostream>
#include <queue>
using namespace std;
#define check(x,y)(x<wx&&x>=0&&y<hy&&y>=0)

struct node {
    int x, y;
};
char room[23][23];
int n, m, wx, hy, num;

int dir[4][2] = {
    {-1, 0}, {0, -1}, {1, 0}, {0, 1}
};

void bfs(int dx, int dy) {
    num = 1;

    queue<node>q;
    node start, next;
    start.x = dx;
    start.y = dy;
    q.push(start);
    while (!q.empty()) {
        start = q.front();
        q.pop();
        // cout<<"out"<<start.x<<' '<<start.y<<endl;
        for (int i = 0; i < 4; i++) {
            next.x = start.x + dir[i][0];
            next.y = start.y + dir[i][1];
            if (check(next.x, next.y) && room[next.x][next.y] == '.') {
                room[next.x][next.y] = '#';
                num++;
                q.push(next);
            }

        }
    }
}

int main() {
    int x, y, dx, dy;
    while (cin >> wx >> hy) {
        if (wx == 0 && hy == 0) {
            break;
        }
        for ( y = 0; y < hy; y++) {
            for (int x = 0; x < wx; x++) {
                cin >> room[x][y];
                if (room[x][y] == '@') {
                    dx = x;
                    dy = y;
                }
            }
        }
        num = 0;
        bfs(dx, dy);
        cout << num << endl;
    }
    return 0;
}