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;
typedef long long ll;
typedef pair<ll, ll> l_l;
typedef pair<int, int> i_i;

#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
//const ll mod = 1000000007;
struct UnionFind {
    vector<int> par;
    vector<int> rank;
    vector<ll> Size;
    UnionFind(int n = 1) {
        init(n);
    }

    void init(int n = 1) {
        par.resize(n + 1); rank.resize(n + 1); Size.resize(n + 1);
        for (int i = 0; i <= n; ++i) par[i] = i, rank[i] = 0, Size[i] = 1;
    }

    int root(int x) {
        if (par[x] == x) {
            return x;
        }
        else {
            int r = root(par[x]);
            return par[x] = r;
        }
    }

    bool issame(int x, int y) {
        return root(x) == root(y);
    }

    bool merge(int x, int y) {
        x = root(x); y = root(y);
        if (x == y) return false;
        if (rank[x] < rank[y]) swap(x, y);
        if (rank[x] == rank[y]) ++rank[x];
        par[y] = x;
        Size[x] += Size[y];
        return true;
    }

    ll size(int x){
        return Size[root(x)];
    }
};


int main() {
    //cout.precision(10);
    cin.tie(0);
    ios::sync_with_stdio(false);
    int field[55][55];
    while(true) {
        int H, W;
        cin >> W >> H;
        if(W == 0 && H == 0) break;
        for(int h = 1; h <= H; h++) {
            for(int w = 1; w <= W; w++) {
                cin >> field[h][w];
            }
        }
        UnionFind uni(3001);
        for(int h = 1; h <= H; h++) {
            for(int w = 1; w <= W; w++) {
                if(field[h][w] == 0) continue; 
                for(int dh = -1; dh <= 1; dh++) {
                    for(int dw = -1; dw <= 1; dw++) {
                        int neww = w + dw;
                        int newh = h + dh;
                        if(neww <= 0 || neww > W || newh <- 0 || newh > H) continue;
                        if(field[newh][neww] == 0) continue;
                        uni.merge(h*50+w, newh*50+neww);
                    }
                }
            }
        }
        int ans = 0;
        for(int h = 1; h <= H; h++) {
            for(int w = 1; w <= W; w++) {
                if(field[h][w] == 0) continue;
                if(uni.root(h*50+w) != h*50+w) continue;
                ans++;
            }
        }
        cout << ans << endl;
    }
    return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstdlib>
#include<vector>
#include<string>
#include<random>
#include<map>
#include<queue>
using namespace std;

vector< vector<int> > bfs(int h, int w, int y, int x, vector< vector<int> > t, int g){
  vector< vector<bool> > b(h, vector<bool> (w, false));
  b[y][x] = true;
  queue< pair<int, int> > q;
  q.push( make_pair(x, y) );
  int dx[8] = {0, 1, 0, -1, 1, -1, 1, -1};
  int dy[8] = {1, 0, -1, 0, 1, -1, -1, 1};
  while(true){
    if( q.empty() ) break;

    pair<int, int> p = q.front();
    q.pop();
    int px = p.first;
    int py = p.second;

    for(int dir=0; dir<8; dir++){
      int tx = px + dx[dir];
      int ty = py + dy[dir];

      if( tx < 0 || tx >= w || ty < 0 || ty >= h ) continue;
      if( b[ty][tx] ) continue;
      if( t[ty][tx] == 0 ) continue;

      b[ty][tx] = true;
      t[ty][tx] = g;
      q.push( make_pair(tx, ty) );
    }
  }

  return t;
}

int main(){

  int w, h;
  while(cin >> w >> h){
    if( w == 0 && h == 0 ) break;
    vector< vector<int> > t(h, vector<int> (w));
    int g = 2;
    for(int i=0; i<h; i++){
      for(int j=0; j<w; j++){
        cin >> t[i][j];
      }
    }

    for(int i=0; i<h; i++){
      for(int j=0; j<w; j++){
        if( t[i][j] == 1 ){
          t = bfs(h, w, i, j, t, g);
          g++;
        }
      }
    }
    cout << g-2 << endl;
  }

  return 0;
}

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

struct Fast {Fast(){std::cin.tie(0);ios::sync_with_stdio(false);}} fast;

/* cpp template {{{ */

/* short */
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second
#define ALL(v) begin(v), end(v)
#define RALL(v) (v).rbegin(), (v).rend()
#define X real()
#define Y imag()

/* REPmacro */
#define REPS(i, a, n) for (ll i = (a); i < (ll)(n); ++i)
#define rep(i, n) REPS(i, 0, n)
#define REP1(i,n) for (ll i = 1; i <= (ll)(n); ++i)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (ll i = (a); i >= (ll)(n); --i)
#define DEP(i, n) DEPS(i, n, 0)
#define EACH(i, n) for (auto&& i : n)

/* debug */
#define debug(x) cerr << x << " " << "(L:" << __LINE__ << ")" << '\n';

/* alias */
using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using D = double;
using P = complex<D>;
using vs = vector<string>;
template <typename T> using PQ = priority_queue<T>;
template <typename T> using minPQ = priority_queue<T, vector<T>, greater<T>>;

/* const */
const int INF = 1001001001;
const ll LINF = 1001001001001001001ll;
const int MOD = 1e9 + 7;
const D EPS = 1e-9;
const int dx[] = {0, 1, 0, -1, 1, -1, 1, -1}, dy[] = {1, 0, -1, 0, 1, -1, -1, 1};

/* func */
inline bool inside(int y, int x, int H, int W) {return y >= 0 && x >= 0 && y < H && x < W;}
inline int in() {int x; cin >> x; return x;}
inline ll IN() {ll x; cin >> x; return x;}
inline vs split(const string& t, char c) {vs v; stringstream s(t); string b; while(getline(s, b, c)) v.eb(b); return v;}
template <typename T> inline bool chmin(T& a, const T& b) {if (a > b) a = b; return a > b;}
template <typename T> inline bool chmax(T& a, const T& b) {if (a < b) a = b; return a < b;}
template <typename T, typename S> inline void print(const pair<T, S>& p) {cout << p.first << " " << p.second << endl;}
template <typename T> inline void print(const T& x) {cout << x << '\n';}
template <typename T, typename S> inline void print(const vector<pair<T, S>>& v) {for (auto&& p : v) print(p);}
template <typename T> inline void print(const vector<T>& v, string s = " ") {rep(i, v.size()) cout << v[i] << (i != (ll)v.size() - 1 ? s : "\n");}

int w,h;
vvi field;
void dfs(int y, int x)
{
  field[y][x]=0;
  rep(i,8)
  {
    int nx=x+dx[i], ny=y+dy[i];
    if(nx<w&&0<=nx&&ny<h&&0<=ny&&field[ny][nx]==1)
    {
      dfs(ny,nx);
    }
  }
}

signed main() 
{
  while(cin>>w>>h, w||h)
  {
    field=vvi(100,vi(100,-1));
    int n;
    rep(y,h) rep(x,w)
    {
      cin>>n;
      field[y][x]=n;
    }
    int x,y;
    int cnt=0;
    rep(y,h) rep(x,w)
    {
      if(field[y][x]==1) 
      {
        dfs(y,x);
        cnt++;
      }
    }
    print(cnt);
  }

  return 0;
}