Time Limit: 1000MS | Memory Limit: 32768KB | 64bit IO Format: %I64d & %I64u |
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
45
59
6
13
Source
Asia 2004, Ehime (Japan), Japan Domestic
思路:裸DFS,扩展到一个点就将答案+1。
AC代码:
#include <cstdio> using namespace std; int w, h, ans; char map[25][25]; const int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0}; struct node { int x, y; }start; bool input() { if (scanf("%d %d\n", &w, &h) == 2 && h) { for (int i = 0; i < h; i++) scanf("%s\n", map[i]); return 1; } return 0; } void dfs(node now) { if (now.x < 0 || now.x >= h || now.y < 0 || now.y >= w || map[now.x][now.y] == '#') return; map[now.x][now.y] = '#'; ans++; node next; for (int i = 0; i < 4; i++) { next.x = now.x + dx[i]; next.y = now.y + dy[i]; dfs(next); } } void solve() { ans = 0; for (int i = 0; i < h; i++) for (int j = 0; j < w; j++) if (map[i][j] == '@') start = (node){i, j}; dfs(start); printf("%d\n", ans); } int main() { while (input()) solve(); return 0; }
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