POJ1979 Red and Black

Red and Black

Time Limit: 1000MS Memory Limit: 30000KTotal Submissions: 23001 Accepted: 12407

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

水

#include <stdio.h>#include <string.h>#define maxn 30char G[maxn][maxn];int n, m, X, Y, sum; // n rows m columns and start positionconst int mov[][2] = {0, 1, 0, -1, 1, 0, -1, 0};void getMap() {    int i, j;    for(i = 0; i < n; ++i) {        scanf("%s", G[i]);        for(j = 0; G[i][j]; ++j)            if(G[i][j] == '@') {                X = i; Y = j;            }    }}bool check(int x, int y) {    if(x < 0 || y < 0 || x >= n || y >= m)        return false;    return G[x][y] == '.';}void DFS(int x, int y) {    G[x][y] = '#'; ++sum;    int i, j, xa, ya;    for(i = 0; i < 4; ++i) {        xa = x + mov[i][0];        ya = y + mov[i][1];        if(check(xa, ya))            DFS(xa, ya);    }}int main() {    // freopen("stdin.txt", "r", stdin);    while(scanf("%d%d", &m, &n), m | n) {        getMap();        sum = 0;        DFS(X, Y);        printf("%d\n", sum);    }    return 0;}