Lake Counting-C++

Description
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.

Input
* 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.

Output
* Line 1: The number of ponds in Farmer John's field.

Sample Input
10 12
W........WW.
.WWW.....WWW
....WW...WW.
.........WW.
.........W..
..W......W..
.W.W.....WW.
W.W.W.....W.
.W.W......W.
..W.......W.
Sample Output
3

CODE:

#include<bits/stdc++.h>
using namespace std;
int cnt=0;
char a[1010][1010];
int dir[8][2]={{1,0},{-1,0},{0,1},{0,-1},{1,1},{1,-1},{-1,1},{-1,-1}};
bool visited[1010][1010];
void dfs(int x,int y)
{
	visited[x][y]=1;
	a[x][y]='.';
	cnt++;
	for(int i=0;i<8;i++)
	{
		int tx=x+dir[i][0];
		int ty=y+dir[i][1];
		if(a[tx][ty]=='W')
		{
			dfs(tx,ty);
		}
	}
}
int main()
{
	int n,m,ans=0;
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
			cin>>a[i][j];
		}
	}
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=m;j++)
		{
			if(a[i][j]=='W')
			{
				cnt=0;
				dfs(i,j);
				ans++;
			}
		}
	}
	cout<<ans<<endl;
}

Thanks for reading.