POJ 2386

Lake Counting

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 29838		Accepted: 14927

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

Hint

OUTPUT DETAILS: 

There are three ponds: one in the upper left, one in the lower left,and one along the right side.

Source

USACO 2004 November

<span style="font-family:Courier New;font-size:18px;"><strong>#include <iostream>
#include <cstdio>
using namespace std;

#define MAX_N 110
#define MAX_M 110

int M, N;
char field[MAX_M][MAX_N];

void Input()
{
    cin >> M >> N;
    for(int i=0; i<M; i++)
        cin >> field[i];
}

void DFS(int x, int y)
{
    field[x][y] = '.';

    for(int move_x = -1; move_x <= 1; move_x++) {
        for(int move_y = -1; move_y <=1 ; move_y++) {
            if(!move_x && !move_y) continue;
            int nx = x + move_x, ny = y + move_y;
            if(0 <= nx && nx < M && 0 <= ny && ny < N && field[nx][ny] == 'W')  DFS(nx, ny);
        }
    }
    return;
}

void Solve()
{
    int res = 0;
    for (int i=0; i<M; i++) {
        for(int j = 0; j<N; j++) {
            if (field[i][j] == 'W') {
                DFS(i, j);
                res++;
            }
        }
    }
    printf("%d\n", res);
}

int main()
{
    Input();
    Solve();
    return 0;
}
/*
10 12
W........WW.
.WWW.....WWW
....WW...WW.
.........WW.
.........W..
..W......W..
.W.W.....WW.
W.W.W.....W.
.W.W......W.
..W.......W.
*/
</strong></span>