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++)
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = 1001001001;
const int MOD = 1000000007;

template <typename T>
void print(const T &v);

vector<vector<int>> grid(55, vector<int>(55, -1));
vector<vector<bool>> seen(55, vector<bool>(55, false));

void dps(int x, int y)
{
    int xs[8] = {1, -1, 0, 0, -1, -1, 1, 1};
    int ys[8] = {0, 0, 1, -1, -1, 1, -1, 1};
    for (int i = 0; i < 8; i++)
    {
        int nx = x + xs[i];
        int ny = y + ys[i];
        if (nx < 0 || ny < 0)
        {
            continue;
        }
        if (seen[nx][ny] || grid[nx][ny] != 1)
        {
            continue;
        }
        seen[nx][ny] = true;
        dps(nx, ny);
    }
}

void init()
{
    for (int i = 0; i < 55; i++)
    {
        for (int j = 0; j < 55; j++)
        {
            grid[i][j] = -1;
            seen[i][j] = false;
        }
    }
}
int main()
{
    while (1)
    {
        int w, h;
        cin >> w >> h;
        if (w == 0 || h == 0)
        {
            return 0;
        }
        init();
        for (int i = 0; i < h; i++)
        {
            for (int j = 0; j < w; j++)
            {
                cin >> grid[i][j];
            }
        }
        int cnt = 0;
        for (int i = 0; i < h; i++)
        {
            for (int j = 0; j < w; j++)
            {
                if (seen[i][j] || grid[i][j] != 1)
                {
                    continue;
                }
                ++cnt;
                dps(i, j);
            }
        }
        cout << cnt << endl;
    }
}

// Use For Debug
template <typename T>
void print(T const &v)
{
    for (int i = 0; i < v.size(); i++)
    {
        if (i)
            cout << ' ';
        cout << v[i];
    }
    cout << endl;
}

C++: #include <cstdio>

using namespace std;

char mp[60][60] = {0};
int dx[9] = {0, 0, 1, -1, 1, -1, 1, -1};
int dy[9] = {1, -1, 0, 0, 1, -1,-1,  1};

void def(int y, int x){
	mp[y][x] = 0;
	for (int i = 0; i < 8; i++){
		int ty = y + dy[i];
		int tx = x + dx[i];
		if (mp[ty][tx] == '1') def(ty, tx);
	}
}

int main()
{
	int w, h;
	int pi, pj;
	int cnt;
	while (scanf("%d %d", &w, &h), !(w == 0 && h == 0)){
		cnt = 0;
		
		for (int i = 0; i < h; i++){
			for (int j = 0; j < w; j++){
				scanf("%s", &mp[i][j]);
			}
		}
		
		for (int i = 0; i < h; i++){
			for (int j = 0; j < w; j++){
				if (mp[i][j] == '1'){
					def(i, j);
					cnt++;
				}
			}
		}
		
		printf("%d\n", cnt);
	}
}