Go: // AOJ 1160: How Many Islands? http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=1160

package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
)

var SEA = 0
var LAND = 1

func nextInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

func discoverIslands(M, V [][]int, H, W int) int {
	// 島を探す
	queue := list.New()
	islands := 0
	for i := 1; i <= H; i++ {
		for j := 1; j <= W; j++ {
			// 訪問済みの土地ならスキップ
			if V[i][j] == 1 {
				continue
			}

			// 訪問中の土地が海なら訪問済みにしてスキップ
			if M[i][j] == SEA {
				V[i][j] = 1
				continue
			}

			// 未訪問の陸地が見つかったので
			// 島の数を1つ増やし、この陸地から辿れる陸地を訪問していく
			islands++
			queue.PushBack([]int{i, j})

			for queue.Len() > 0 {
				cur := queue.Remove(queue.Front()).([]int)
				h, w := cur[0], cur[1]
				if V[h][w] == 1 {
					continue
				}
				V[h][w] = 1

				// 全方向に未訪問の陸地がないか探索
				for v := -1; v <= 1; v++ {
					for l := -1; l <= 1; l++ {
						dh := h + v
						dw := w + l
						if M[dh][dw] == LAND && V[dh][dw] == 0 {
							queue.PushBack([]int{dh, dw})
						}
					}
				}
				/*
					if M[h-1][w] == LAND {
						queue.PushBack([]int{h - 1, w})
					}
					if M[h-1][w+1] == LAND {
						queue.PushBack([]int{h - 1, w + 1})
					}
					if M[h][w+1] == LAND {
						queue.PushBack([]int{h, w + 1})
					}
					if M[h+1][w+1] == LAND {
						queue.PushBack([]int{h + 1, w + 1})
					}
					if M[h+1][w] == LAND {
						queue.PushBack([]int{h + 1, w})
					}
					if M[h+1][w-1] == LAND {
						queue.PushBack([]int{h + 1, w - 1})
					}
					if M[h][w-1] == LAND {
						queue.PushBack([]int{h, w - 1})
					}
					if M[h-1][w-1] == LAND {
						queue.PushBack([]int{h - 1, w - 1})
					}
				*/
			}
		}
	}
	return islands
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	for {
		W, H := nextInt(sc), nextInt(sc)

		if W == 0 && H == 0 {
			break
		}
		// Initialize map and visted list
		M := make([][]int, H+2)
		V := make([][]int, H+2)
		for i := 0; i < H+2; i++ {
			M[i] = make([]int, W+2)
			V[i] = make([]int, W+2)
		}
		for i := 1; i <= H; i++ {
			for j := 1; j <= W; j++ {
				M[i][j] = nextInt(sc)
			}
		}

		islands := discoverIslands(M, V, H, W)

		fmt.Println(islands)
	}
}

C++: #include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repi(i, a, b) for (int i = int(a); i < int(b); ++i)
typedef long long ll;
long long mod = 1e9 + 7;
const long long INF = 1LL << 60;
using namespace std;

template <class T>
inline bool chmin(T &a, T b)
{
    if (a > b)
    {
        a = b;
        return true;
    }
    return false;
}

template <class T>
inline bool chmax(T &a, T b)
{
    if (a < b)
    {
        a = b;
        return true;
    }
    return false;
}

int wi, he;
int c[100][100];
bool seen[100][100];

void dfs(int w, int h)
{
    if (c[w][h] == 1 && seen[w][h] == false)
    {
        seen[w][h] = true;
        if (c[w + 1][h] == 1)
        {
            dfs(w + 1, h);
        }

        if (c[w - 1][h] == 1)
        {
            dfs(w - 1, h);
        }

        if (c[w][h - 1] == 1)
        {
            dfs(w, h - 1);
        }

        if (c[w][h + 1] == 1)
        {
            dfs(w, h + 1);
        }

        if (c[w + 1][h + 1] == 1)
        {
            dfs(w + 1, h + 1);
        }

        if (c[w + 1][h - 1] == 1)
            dfs(w + 1, h - 1);

        if (c[w - 1][h + 1] == 1)
            dfs(w - 1, h + 1);

        if (c[w - 1][h - 1] == 1)
            dfs(w - 1, h - 1);
    };
}

int main()
{
    vector<int> res;
    while (true)
    {
        int ans = 0;

        rep(i, 100) rep(j, 100)
        {
            c[i][j] = 0;
            seen[i][j] = 0;
        }

        cin >> wi >> he;
        if (wi == 0 && he == 0)
            break;

        repi(j, 1, he + 1) repi(i, 1, wi + 1)
        {
            cin >> c[i][j];
        };

        repi(i, 1, wi + 1) repi(j, 1, he + 1)
        {
            if (c[i][j] == 1 && seen[i][j] == false)
            {
                dfs(i, j);
                ans++;
            }
        }

        res.push_back(ans);
    }

    for (auto r : res)
    {
        cout << r << endl;
    }
    return 0;
}

C++: #include <bits/stdc++.h>
#define debug(x) cerr << #x << ": " << x << '\n';
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = (int)1e9;

int w, h;
int c[51][51];
int dx[] = {1, -1, 0, 0, 1, 1, -1, -1};
int dy[] = {0, 0, 1, -1, 1, -1, 1, -1};

void dfs(int y, int x){
	c[y][x] = 0;
	for(int i = 0; i < 8; i++){
		int ny = y + dy[i], nx = x + dx[i];
		if(0<=ny and ny<h and 0<=nx and nx<w and c[ny][nx]==1){
			dfs(ny, nx);
		}
	}
}

int solve(){
	int res = 0;
	for(int i = 0; i < h; i++){
		for(int j = 0; j < w; j++){
			if(c[i][j] == 1){
				dfs(i, j);
				res++;
			}
		}
	}

	return res;
}

int main(void){
	while(scanf("%d%d", &w, &h) != EOF){
		if(w == 0 and h == 0) break;
		for(int i = 0; i < h; i++){
			for(int j = 0; j < w; j++){
				scanf("%d", &(c[i][j]));
			}
		}
		printf("%d\n", solve());
	}

	return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;

const int MAX_H = 50;
const int MAX_W = 50;
int field[MAX_H][MAX_W];
int cnt;
int H, W;
// int dy[4] = {1, 0, -1, 0};
// int dx[4] = {1, 1, 0, -1};
bool seen[MAX_H][MAX_W];

void bfs(int y, int x)
{
    for (int dy = -1; dy <= 1; dy++)
    {
        for (int dx = -1; dx <= 1; dx++)
        {
            if (dy == 0 && dx == 0)
                continue;

            int ny = y + dy;
            int nx = x + dx;
            if (ny < 0 || ny >= H || nx < 0 || nx >= W)
                continue;
            if (field[ny][nx] == 0)
                continue;
            if (seen[ny][nx])
                continue;

            seen[ny][nx] = true;
            bfs(ny, nx);
        }
    }
}

int main()
{

    while (true)
    {
        cin >> W >> H;
        if (W == 0 && H == 0)
            break;

        for (int y = 0; y < H; y++)
        {
            for (int x = 0; x < W; x++)
            {
                cin >> field[y][x];
            }
        }

        cnt = 0;
        for (int y = 0; y < H; y++)
        {
            for (int x = 0; x < W; x++)
            {
                seen[y][x] = false;
            }
        }

        for (int y = 0; y < H; y++)
        {
            for (int x = 0; x < W; x++)
            {
                if (seen[y][x] || field[y][x] == 0)
                    continue;
                cnt++;
                seen[y][x] = true;
                bfs(y, x);
            }
        }

        cout << cnt << endl;
    }

    return 0;
}