poj1979

Red and Black

Time Limit: 1000MS Memory Limit: 30000KTotal Submissions: 22582 Accepted: 12185

Description

There is a rectangular room, covered with square tiles. Each tile is colored either red or black. A man is standing on a black tile. From a tile, he can move to one of four adjacent tiles. But he can't move on red tiles, he can move only on black tiles.

Write a program to count the number of black tiles which he can reach by repeating the moves described above.

Input

The input consists of multiple data sets. A data set starts with a line containing two positive integers W and H; W and H are the numbers of tiles in the x- and y- directions, respectively. W and H are not more than 20.

There are H more lines in the data set, each of which includes W characters. Each character represents the color of a tile as follows.

'.' - a black tile
'#' - a red tile
'@' - a man on a black tile(appears exactly once in a data set)
The end of the input is indicated by a line consisting of two zeros.

Output

For each data set, your program should output a line which contains the number of tiles he can reach from the initial tile (including itself).

Sample Input

6 9....#......#..............................#@...#.#..#.11 9.#..........#.#######..#.#.....#..#.#.###.#..#.#..@#.#..#.#####.#..#.......#..#########............11 6..#..#..#....#..#..#....#..#..###..#..#..#@...#..#..#....#..#..#..7 7..#.#....#.#..###.###...@...###.###..#.#....#.#..0 0

Sample Output

4559613

Source

Japan 2004 Domestic


哎，长时间不a题，简单的dfs都不会了。。。郁闷。。。。。以后还是要每天保持a题量。。。。

#include <iostream>#include <cstdio>using namespace std;char mp[21][21];int dis[4][2] = {{0,1},{1,0},{-1,0},{0,-1}};int sum,w,h;void dfs(int x,int y){    for(int i = 0; i < 4; i++)    {        int xx = x + dis[i][0];        int yy = y + dis[i][1];        if(xx >= 1 && xx <= h && yy >=  1 && yy <=  w  &&  mp[xx][yy] == '.')        {            sum++;            mp[xx][yy] = '#';            dfs(xx,yy);        }    }}int main(){    //freopen("in","r",stdin);    while(cin>>w>>h,w+h)    {        int x,y;        sum = 1;        for(int i = 1; i <= h; i++)            for(int j = 1; j <= w; j++)            {                cin>>mp[i][j];                if(mp[i][j] == '@')                {                    x = i;                    y = j;                }            }        dfs(x,y);        cout<<sum<<endl;    }    return 0;}