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 <stdio.h>

void solve(int a[50][50],int x,int y){
	int i, j;
	a[y][x] = 0;
	for(i = y - 1;i <= y + 1;i++){
		for(j = x - 1;j <= x + 1;j++)
			if(a[i][j]) solve(a,j,i);
	}
	return;
}

int main(void){
	int w, h, i, j, flag[50][50], count;
	scanf("%d%d",&w,&h);
	while(w != 0 || h != 0){
		for(i = 0;i < h;i++)
			for(j = 0;j < w;j++) scanf("%d",&flag[i][j]);
		count = 0;
		for(i = 0;i < h;i++){
			for(j = 0;j < w;j++){
				if(flag[i][j]){
					count++;
					solve(flag,j,i);
				}
			}
		}
		printf("%d\n",count);
		scanf("%d%d",&w,&h);
	}
	return 0;
}

C++: #include <iostream>
#define MAX_W 50
#define MAX_H 50
using namespace std;

int w, h;
int t[MAX_H][MAX_W];

void PRINT() {
  for(int i = 0; i < h; ++i) {
    for(int j = 0; j < w; ++j) {
      cout << t[i][j] << ' ';
    }
    cout << endl;
  }
  cout << endl;
}

// 深さ優先探索
// 現在位置(y, x)
void dfs(int y, int x) {
  t[y][x] = 8;

  for(int dx = -1; dx <= 1; dx++) {
    for(int dy = -1; dy <= 1; dy++) {
      // 現在位置を(nx, ny)に更新
      int nx = x + dx;
      int ny = y + dy;

      // (nx, ny)は部屋の中か？ & t[nx][ny]は陸か？ を判定
      if(0 <= nx && nx < w && 0 <= ny && ny < h && t[ny][nx] == 1) {
        dfs(ny, nx);
        //PRINT();
      }
    }
  }
  return;
}

void solve() {
  int cnt = 0;
  for(int y = 0; y < h; ++y) {
    for(int x = 0; x < w; ++x) {

      if(t[y][x] == 1) {
        dfs(y, x);
        cnt++;
      }
      
    }
  }
  cout << cnt << endl;
}

int main() {
  while(cin >> w >> h && w && h) {

    for(int i = 0; i < h; ++i) {
      for(int j = 0; j < w; ++j) {
        cin >> t[i][j];
      }
    }
    solve();
  }
  return 0;
}

C++: #define _crt_secure_no_warnings

#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>

#ifdef __GXX_EXPERIMENTAL_CXX0X__
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif


#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>

#ifdef __GXX_EXPERIMENTAL_CXX0X__
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif

using namespace std;

vector<vector<int>>data;

int x[] = { 0, 1, 1, 1, 0, -1, -1, -1 };
int y[] = { 1, 1, 0, -1, -1, -1, 0, 1 };

void serch(int i, int j)
{
	data[i][j] = 0;
	for (size_t k = 0; k < 8; k++)
	{
		if (data[i + x[k]][j + y[k]])
		{
			serch(i + x[k], j + y[k]);
		}
	}
}

int main()
{
	int N, M;
	int ans = 0;
	while (1)
	{
		data.clear();
		ans = 0;
		cin >> N >> M;
		if (N == 0 && M == 0)break;
		swap(M, N);
		data.resize(N + 2);
		for (size_t i = 0; i < N + 2; i++)
		{
			data[i].resize(M + 2);
			for (size_t j = 0; j < M+2; j++)
			{
				data[i][j] = 0;
			}
		}
		for (size_t i = 1; i <= N; i++)
		{
			for (size_t j = 1; j <= M; j++)
			{
				cin >> data[i][j];
			}
		}
		for (size_t i = 1; i <= N; i++)
		{
			for (size_t j = 1; j <= M; j++)
			{
				if (data[i][j])
				{
					ans++;
					serch(i, j);
				}
			}
		}
		cout << ans<<endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) FOR(i,0,n)
#define repr(i,n) for(int i=(n)-1;0<=i;--i)
#define each(e,v) for(auto&& e:(v))
#define all(v) begin(v),end(v)
#define dump(x) cerr<<#x<<": "<<(x)<<endl
#define INF 100000000
#define IINF 9999999999999;
using vint = vector<int>;
using ll = long long;
using vll = vector<ll>;
template <class T> void chmin(T& a, const T& b) { a = min(a, b); }
template <class T> void chmax(T& a, const T& b) { a = max(a, b); }

int prime[25] = {2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97};
long long int dp[101][20] = {0};

bool earth[51][51];

void erase_island(int h, int w) {
    earth[h][w] = false;
    //cout << "# " << h << " " << w << endl;
    if(earth[h - 1][w - 1]) erase_island(h - 1, w - 1);
    if(earth[h - 1][w]) erase_island(h - 1, w);
    if(earth[h - 1][w + 1]) erase_island(h - 1, w + 1);
    if(earth[h][w + 1]) erase_island(h, w + 1);
    if(earth[h + 1][w + 1]) erase_island(h + 1, w + 1);
    if(earth[h + 1][w]) erase_island(h + 1, w);
    if(earth[h + 1][w - 1]) erase_island(h + 1, w - 1);
    if(earth[h][w - 1]) erase_island(h, w - 1);
}

int main() {
    int w, h;
    cin >> w >> h;
    rep(i, h) rep(j, w) {
        int temp;
        cin >> temp;
        if(temp == 0) earth[i][j] = false;
        else earth[i][j] = true;
    }

    int ans = 0;
    rep(i, h) rep(j, w) {
        if(earth[i][j]) erase_island(i , j), ++ans;
    }

    cout << ans << endl;
}