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 <iostream>
#include <cmath>
#include <string>
#include <utility>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#define debug(x) cerr << #x << ':' << x << endl
using namespace std;
typedef long long ll;

int dx[8]={1,1,0,-1,-1,-1,0,1}, dy[8]={0,1,1,1,0,-1,-1,-1};
void dfs(int x, int y, int Map[51][51], int h, int w){
    if(!(0<=x && x <=h-1 && 0<=y && y<=w && Map[x][y]==1)) return;
    Map[x][y]=0;
    for(int i=0; i<8; i++)
        dfs(x+dx[i], y+dy[i], Map, h, w);
}

void disp(int Map[51][51], int h, int w){
    cout << "==========" << endl;
    for(int x=0; x<=h-1; x++){
        for(int y=0; y<=w-1; y++) cout << Map[x][y] << "";
        cout << endl;
    }
    cout << "==========" << endl;
}

int main(){
    int Map[51][51]={};
    int h, w;
    while(1){
        cin >> w >> h;
        if(h == 0 && w ==0) break;
        for(int x=0; x<=h-1; x++)
            for(int y=0; y<w; y++)
                cin >> Map[x][y];
        
        int cnt=0;
        for(int x=0; x<=h-1; x++)
            for(int y=0; y<w; y++){
                // cout << "before" << endl;
                // disp(Map, h, w);
                if(Map[x][y]==1) dfs(x, y, Map, h, w), cnt++;
                // cout << "after" << endl;
                // disp(Map, h, w);
            }
                
        
        cout << cnt << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <fstream>
#include <set>
#include <map>
#include <vector>
#include <algorithm>
#include <cmath>
#include <chrono>
using namespace std;

void connection(vector<vector<bool>> &checked, int i, int j, int h, int w) {
    if (!checked.at(i).at(j)) return;
    checked.at(i).at(j) = false;
    for (int x = max(0, i - 1); x <= min(h - 1, i + 1); x++) {
        for (int y = max(0, j - 1); y <= min(w - 1, j + 1); y++) {
            if (x != i || y != j) connection(checked, x, y, h, w);
        }
    }
    return;
}

int main(int argc, const char * argv[]) {
    
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    while(true) {
        int w, h;
        cin >> w >> h;
        if (h == 0 && w == 0) break;
        
        vector<vector<bool>> checked(h, vector<bool>(w, false));
        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {
                bool a;
                cin >> a;
                checked.at(i).at(j) = a;
            }
        }
        
        int ans = 0;
        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {
                if (checked.at(i).at(j)) {
                    connection(checked, i, j, h, w);
                    ans++;
                }
            }
        }
        
        cout << ans << endl;
    }
    
    return 0;
}

C++: #include <cstdio>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <vector>
#include <array>
#include <map>
#include <set>
using namespace std;

#define IS_POWER_TWO(x) (!(x & (x-1))) 
struct UnionFind {
	vector<int> data;
	UnionFind(int size) : data(size, -1) { }
	bool unionSet(int x, int y) {
		x = root(x); y = root(y);
		if (x != y) {
			if (data[y] < data[x]) swap(x, y);
			data[x] += data[y]; data[y] = x;
		}
		return x != y;
	}
	bool findSet(int x, int y) {
		return root(x) == root(y);
	}
	int root(int x) {
		return data[x] < 0 ? x : data[x] = root(data[x]);
	}
	int size(int x) {
		return -data[root(x)];
	}
};

typedef pair<int, int> pii;
const pii Dir_eight[8]{
	{0,-1},{-1,0},{1,0},{0,1},{-1,-1},{1,1},{-1,1},{1,-1}
};

int main()
{
	int w, h;

	while (scanf("%d %d", &w, &h)) {
		if (w == 0)
			return 0;
		array<array<int, 52>, 52> map = {};
		UnionFind uf(2501);

		for (int i = 0; h > i; i++) {
			for (int j = 0; w > j; j++) {
				int a;
				scanf("%d", &a);

				map[j + 1][i + 1] = a;
				if (!a)uf.unionSet(i*w + j, h*w);
			}
		}

		for (int i = 1; h >= i; i++) {
			for (int j = 1; w >= j; j++) {
				if (map[j][i]) {
					for (int k = 0; 8 > k; k++) {
						if (map[j + Dir_eight[k].first][i + Dir_eight[k].second]) {
							uf.unionSet(j + Dir_eight[k].first + (i + Dir_eight[k].second-1)*w-1, (i-1)*w + j-1);
						}
					}
				}
			}
		}

		set<int> ver;

		for (int i = 0; h*w+1 > i; i++) {
			ver.insert(uf.root(i));
		}
		
		printf("%d\n", ver.size() - 1);
	}
	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <utility>
#include <memory>
#include <functional>
#include <deque>
#include <cctype>
#include <numeric>
#include <ctime>
#include <bitset>
#include <cctype>
#include <vector>
#include <map>
#include <set>
#include <stack>
#include <queue>
#include <cstring>
#include <string>
#include <sstream>
#include <algorithm>
#include <iomanip>

using namespace std;

//define
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#define dump(x)  cerr << #x << " = " << (x) << endl;

#define INF (INT_MAX/3)
#define PI (2*acos(0.0))
#define EPS (1e-8)
#define MOD (1000000007LL)

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

typedef vector<int> vint;
typedef vector<vector<int> > vvint;
typedef vector<ll> vll;
typedef vector<vector<ll> > vvll;

#define vv(t) vector< vector< T > >
#define pb push_back
#define pu push
#define fi first
#define sec second
#define SORT(x) sort((x).begin(),(x).end())
#define EQ(a,b) (abs((a)-(b))<EPS)

int w, h;
char field[50][50];
typedef pair<int, int> P;

void bfs(int sh, int sw){
  queue<P> que;
  que.push(P(sh, sw));
  while(!que.empty()){
    P p = que.front();
    que.pop();
    int nh = p.first, nw = p.second;
    field[nh][nw] = '0';
    for(int i = -1; i <= 1; i++){
      for(int j = -1; j <= 1; j++){
        if(i == 0 && j == 0) continue;
        int th = nh + i, tw = nw + j;
        if(th < 0 || th >= h || tw < 0 || tw >= w || field[th][tw] != '1') continue;
        que.push(P(th, tw));
      }
    }
  }
}

int main(void){
  ios_base::sync_with_stdio(0);
  while(cin >> w >> h, w || h){
    for(int i = 0; i < h; i++){
      for(int j = 0; j < w; j++) cin >> field[i][j];
    }
    int ans = 0;
    for(int i = 0; i < h; i++){
      for(int j = 0; j < w; j++){
        if(field[i][j] == '0') continue;
        bfs(i, j);
        ans++;
      }
    }
    cout << ans << endl;
  }
  return 0; 
}