POJ 2386 Lake Counting（水坑计数）

Due to recent rains, water has pooled in various places in Farmer John’s field, which is represented by a rectangle of N x M (1 <= N <= 100; 1 <= M <= 100) squares. Each square contains either water (‘W’) or dry land (‘.’). Farmer John would like to figure out how many ponds have formed in his field. A pond is a connected set of squares with water in them, where a square is considered adjacent to all eight of its neighbors.

Given a diagram of Farmer John’s field, determine how many ponds he has.

Line 1: Two space-separated integers: N and M

Lines 2..N+1: M characters per line representing one row of Farmer John’s field. Each character is either ‘W’ or ‘.’. The characters do not have spaces between them.

Line 1: The number of ponds in Farmer John’s field.

思路：“漫水填充” 深度优先搜索

CODE:

int N, M;
char field[100][100];
void dfs(int x, int y)
{
field[x][y] = '.';

for (int dx = -1; dx <= 1; ++dx)
for (int dy = -1; dy <= 1; ++dy)
{
int nx, ny;
nx = x + dx; ny = y + dy;
if (0 <= nx&&nx <= N && 0 <= ny&&ny <= M&&field[nx][ny] == 'W')
dfs(nx, ny);
}
return;
}
void solve()
{
int n = 0;
for (int x = 0; x < N; ++x)
for (int y = 0; y < M; ++y)
{
if (field[x][y] == 'W')
{
dfs(x, y);
++n;
}
}
cout << n;
}