Go: ///
// File:  1160.go
// Author: ymiyamoto
//
// Created on Sun Mar  4 20:45:57 2018
//
package main

import (
	"fmt"
)

var w, h int
var graph [][]string

func dfs(visited [][]bool, x, y int) {
	visited[x][y] = true

	for i := -1; i <= 1; i++ {
		for j := -1; j <= 1; j++ {
			dx := x + i
			dy := y + j
			if 0 <= dx && dx < h && 0 <= dy && dy < w && graph[dx][dy] == "1" && !visited[dx][dy] {
				dfs(visited, dx, dy)
			}
		}
	}
}

func main() {
	for {
		fmt.Scan(&w, &h)
		if w == 0 && h == 0 {
			break
		}

		graph = make([][]string, h)
		for i := range graph {
			graph[i] = make([]string, w)
		}

		for i := 0; i < h; i++ {
			for j := 0; j < w; j++ {
				var s string
				fmt.Scan(&s)
				graph[i][j] = s
			}
		}

		visited := make([][]bool, h)
		for i := range visited {
			visited[i] = make([]bool, w)
		}

		count := 0
		for i := range graph {
			for j := range graph[i] {
				if graph[i][j] == "1" && !visited[i][j] {
					dfs(visited, i, j)
					count++
				}
			}
		}

		fmt.Println(count)
	}
}

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); }

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() {
    ofstream outputfile("output.txt");
    int w, h;
    while(cin >> w >> h, w + h) {
        if(w == 0 && h == 0) break;
        int temp;
        rep(i, h) {
            rep(j, w) {
                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;
                }
            }
        }

        outputfile << ans << endl;
    }

    return 0;
}

C++: #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>

#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif

// C++
#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>

#if __cplusplus >= 201103L
#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 <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif




#define int long long
#define rng(i,l,r) for(size_t i=(l);i<(r);++i)
#define rep(i,n) rng(i,0,n)
#define gnr(i,l,r) for(size_t i=(r)-1;i>=(l);i--)
#define per(i,b) gnr(i,0,b)
#define ALL(obj) (obj).begin(), (obj).end()   //1,2,3,...
#define rALL(obj) (obj).rbegin(), (obj).rend()//...,3,2,1

using namespace std;


//constant
const int MOD = 1e9+7;
const int INF = 1e18;
const int dx4[4] = {1, 0, -1, 0};
const int dy4[4] = {0, 1, 0, -1};
const int dx8[8] = {1,1,0,-1,-1,-1,0,1};
const int dy8[8] = {0,1,1,1,0,-1,-1,-1};
const double pi = acos(-1);


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 gcd(int a,int b){return b?gcd(b,a%b):a;}
//*max_element(ALL(vector))
//count(ALL(vector),num) -> n
//memset(obj,value,sizeof(obj));
int H,W;


void dfs(int h,int w,int map[60][60],int seen[60][60]){
    
    if(seen[h][w]) return;
    
    seen[h][w] = true;
    
    for (int i = 0; i < 8; i++) {
        int nh = h+dy8[i];
        int nw = w+dx8[i];
        bool ishok = (0<=nh && nh<H);
        bool iswok = (0<=nw && nw<W);
        bool island= (map[nh][nw]);
        
        if(seen[nh][nw]) continue;
        if(!(ishok&&iswok&&island)) continue;
        
        dfs(nh,nw,map,seen);
        
    }
}

void solve(){
    
    // remove the bottom 3 lines when you submit this code.
    std::ifstream in("sample.txt");
    std::cin.rdbuf(in.rdbuf());

    cin.tie(0);
    ios::sync_with_stdio(false);
    
    
    while(cin >> W >> H){
        if(W==0&&H==0) break;
        int map[60][60]; memset(map,0,sizeof(map));
        int seen[60][60];memset(seen,false,sizeof(seen));
        for (int h = 0; h < H; h++) {for (int w = 0; w < W; w++) cin >> map[h][w];}
        
        int ans = 0;
        for (int h = 0; h < H; h++) {
            for (int w = 0; w < W; w++) {
                if(!map[h][w] || seen[h][w]) continue;
                dfs(h,w,map,seen);
                ans++;
            }
        }
        
        cout << ans << endl;
        
        
    }
    
}





signed main() {
    solve();
    return 0;
}

C++: #include <bits/stdc++.h>
#define INF 1000000000
using namespace std;

vector<pair<int, int>> bfs(vector<pair<int, int>> not_yet, vector<vector<int>> maze)
{
  pair<int, int> check = not_yet.at(0);
  queue<pair<int, int>> a;
  a.push(check);
  maze.at(check.first).at(check.second) = 0;
  while (!a.empty())
  {
    pair<int, int> now = a.front();
    a.pop();
    not_yet.erase(find(not_yet.begin(), not_yet.end(), now));
    vector<int> move = {1, 0, -1};
    for (int i = 0; i < 3; ++i)
    {
      for (int j = 0; j < 3; ++j)
      {
        if (i == 1 && j == 1)
        {
          continue;
        }
        if (maze.at(now.first + move.at(i)).at(now.second + move.at(j)) == 1)
        {
          a.push({now.first + move.at(i), now.second + move.at(j)});
          maze.at(now.first + move.at(i)).at(now.second + move.at(j)) = 0;
        }
      }
    }
  }
  return not_yet;
}

int main()
{
  while (true)
  {
    int w, h;
    cin >> w >> h;
    if (w == h && w == 0)
    {
      break;
    }
    vector<vector<int>> maze(h + 2, vector<int>(w + 2, -1));
    vector<pair<int, int>> not_yet(0);// h w
    for (int i = 1; i < h + 1; ++i)
    {
      for (int j = 1; j < w + 1; ++j)
      {
        int point;
        cin >> point;
        maze.at(i).at(j) = point;
        if (point == 1)
        {
          not_yet.push_back({i, j});
        }
      }
    }

    int ans = 0;
    while (not_yet.size() != 0)
    {
      not_yet = bfs(not_yet, maze);
      ans += 1;
    }
    cout << ans << endl;
  }
}