ZOJ-2165（DFS）

Red and Black

Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 65536/32768K (Java/Other)

Total Submission(s) : 67   Accepted Submission(s) : 49

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Problem 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) 

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

Asia 2004, Ehime (Japan), Japan Domestic

连通块问题，

当初怎么改都没改出来，

突然发现是先列后行。。

思路与最大黑区域相同：

#include <iostream>#include <stdio.h>#include <string.h>using namespace std;int Map[21][21];char s[21][21];int n,m;int ax,ay;int cnt;int dir[4][2]={1,0,-1,0,0,1,0,-1};int mx;int my;void dfs(int x,int y){       for(int i=0;i<4;i++)       {           mx=x+dir[i][0];           my=y+dir[i][1];           if(Map[mx][my]==1&&mx>=0&&my>=0&&mx<n&&my<m)           {               cnt++;               Map[mx][my]=0;               dfs(mx,my);           }       }}int main(){    while(~scanf("%d%d",&m,&n)&&n&&m)    {        cnt=1;        memset(Map,0,sizeof(Map));        for(int i=0;i<n;i++)        {            for(int j=0;j<m;j++)            {                cin>>s[i][j];                if(s[i][j]=='@')                {                    ax=i;                    ay=j;                }                if(s[i][j]=='.')                {                    Map[i][j]=1;                }            }        }        Map[ax][ay]=0;        dfs(ax,ay);        cout<<cnt<<endl;    }    return 0;}