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<int, int> duo;

#define TT template<typename T>
TT T    sq(T x){ return x*x; }
TT int  ubnd(vector<T>& v,T x){ return upper_bound(v.begin(), v.end(), x) - v.begin(); }
TT int  lbnd(vector<T>& v,T x){ return lower_bound(v.begin(), v.end(), x) - v.begin(); }
TT void sort(T& v){ sort(v.begin(), v.end()); }
TT void revs(T& v){ reverse(v.begin(), v.end()); }
TT void uniq(T& v){ sort(v); v.erase(unique(v.begin(), v.end()), v.end()); }
TT void show(T& v,char d=' ',char e='\n'){for(int i=0;i<v.size();++i)cout<<v[i]<<((i==v.size()-1)?e:d);}
TT void inpt(vector<T>& v,int n){ v.reserve(n);for(int i=0;i<n;++i){T x; cin>>x; v.push_back(x);} }
TT T    In(T& x){ cin >> x; return x; }

static inline void fast_io(){ ios::sync_with_stdio(0); cin.tie(0); }
static inline int in(){ int x; scanf("%d", &x); return x; }
static inline string instr(){ string x; cin >> x; return x; }
static const int dx[] = {0, 0, 1, -1, 1, 1, -1, -1};
static const int dy[] = {1, -1, 0, 0, 1, -1, 1, -1};

struct Solver {
  Solver(int w, int h) : w(w), h(h) { memset(field, 0, sizeof(field)); }
  void input(){
    for (int y = 0; y < h; y++){
      for (int x = 0; x < w; x++){
        field[y][x] = in();
      }
    }
  }
  int solve(){
    int count = 0;
    for (int y = 0; y < h; y++){
      for (int x = 0; x < w; x++){
        if (field[y][x]){
          count++;
          erase(x, y);
        }
      }
    }
    return count;
  }

  void erase(int x, int y){
    if (invalid(x, y)) return;
    if (!field[y][x]) return;
    field[y][x] = 0;
    for (int d = 0; d < 8; d++){
      erase(x + dx[d], y + dy[d]);
    }
  }
  bool invalid(int x, int y){
    return x < 0 || w <= x || y < 0 || h <= y;
  }
  const int w, h;
  int field[64][64];
};

int main()
{
  int w, h;
  while (w = in(), h = in()){
    Solver s(w, h);
    s.input();
    printf("%d\n", s.solve());
  }
  return (0);
}

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

int w,h;
int maps[50][50];

void dfs(int y, int x)
{
  int dx[]={1,-1,0,0};
  int dy[]={0,0,1,-1};

  maps[y][x]=0;

  for(int i=0;i < 4;i++){
    for(int j=0;j < 4;j++){
      int xx = x + dx[j];
      int yy = y + dy[i];
      if(maps[yy][xx] == 1 && xx >= 0 && xx < w && yy >= 0 && yy < h) dfs(yy,xx);
    }
  }
}

int main(){
  while(cin >> w >> h && w)
    {
      for(int i=0;i < h;i++){
	for(int j=0;j < w;j++){
	  cin >> maps[i][j];
	}
      }
      int island=0;

      for(int i=0;i < h;i++){
	for(int j=0;j < w;j++){
	  if(maps[i][j] == 1){
	    island++;
	    dfs(i,j);
	  }
	}
      }
      cout << island << endl;
    }
  return 0;
}

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

static const int MAX_H = 50;
static const int MAX_W = 50;

int H, W;
char grid[MAX_H][MAX_W + 1];
bool reached[MAX_H][MAX_W];

#define OCTAS
#ifdef OCTAS
static const int dh[]{-1, -1, -1, 0, 0, +1, +1, +1};
static const int dw[]{-1, 0, +1, -1, +1, -1, 0, +1};
#else
static const int dh[]{-1, 0, 0, +1};
static const int dw[]{0, -1, +1, 0};
#endif

bool dfs(int h, int w) {
  reached[h][w] = true;

  for (int i{}; i < sizeof(dh) / sizeof(int); ++i) {
    int nh = h + dh[i];
    if (nh < 0 || nh >= H)
      continue;
    int nw = w + dw[i];
    if (nw < 0 || nw >= W)
      continue;
    if (grid[nh][nw] == '0' || reached[nh][nw])
      continue;
    if (dfs(nh, nw))
      return true;
  }

  return false;
}

int main() {
  while (true) {
    cin >> W >> H;
    if (W == 0 && H == 0) break;
    for (int h{}; h < H; ++h) {
      for (int w{}; w < W; ++w) {
        cin >> grid[h][w];
      }
    }
    fill_n(reached[0], MAX_H * MAX_W, false);
    int count{};
    for (int h{}; h < H; ++h) {
      for (int w{}; w < W; ++w) {
        if (grid[h][w] == '0' || reached[h][w])
          continue;
        dfs(h, w);
        ++count;
      }
    }
    cout << count << endl;
  }
}

C++: // C++ 14
#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <algorithm>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <unordered_map>
#include <math.h>

#define ll long long
#define Int ll
#define loop(__x, __start, __end) for(Int __x = __start; __x < __end; __x++)
#define loopdown(__x, __start, __end) for(Int __x = __start; __x > __end; __x--)
#define rep(__n) for(Int __x = 0; __x < __n; __x++)
#define span(__a,__x,__y) __a.begin()+__x,__a.begin()+__y
#define span_all(__a) __a.begin(),__a.end()
#define len(__x) (__x.size())
#define last(__x) (__x[__x.size()-1])

using namespace std;

struct Point {
  Int x, y;
  Point(Int x, Int y): x(x), y(y) {}
  Point(): x(0), y(0) {}

  bool operator< (const Point &p1) const {
    return x < p1.x && y < p1.y;
  }
};
ostream & operator << (ostream & out, Point const & v) {
  out << "Point(" << v.x << ", " << v.y << ')';
  return out;
}

istream & operator >> (istream & in, Point & v) {
  Int x, y;
  in >> x; in >> y; v.x = x; v.y = y;
  return in;
}

// Geometry

#define EPS 0.0000000001

class Vector2 {
public:
  double x, y;
  
  Vector2(double x = 0, double y = 0): x(x), y(y) {}
  
  Vector2 operator + (Vector2 v) { return Vector2(x + v.x, y + v.y); }
  Vector2 operator - (Vector2 v) { return Vector2(x - v.x, y - v.y); }
  Vector2 operator * (double k) { return Vector2(x * k, y * k); }
  Vector2 operator / (double k) { return Vector2(x / k, y / k); }
  
  double length() { return sqrt(norm()); }
  double norm() { return x * x + y * y; }
  double dot (Vector2 v) { return x * v.x + y * v.y; }
  double cross (Vector2 v) { return x * v.y - y * v.x; }
  
  bool operator < (const Vector2 &v) const {
    return x != v.x ? x < v.x : y < v.y;
  }
  
  bool operator == (const Vector2 &v) const {
    return fabs(x - v.x) < EPS && fabs(y - v.y) < EPS;
  }
};

ostream & operator << (ostream & out, Vector2 const & v) { 
  out<< "Vector2(" << v.x << ", " << v.y << ')';
  return out;
}

istream & operator >> (istream & in, Vector2 & v) { 
  double x, y;
  in >> x;
  in >> y;
  v.x = x;
  v.y = y;
  return in;
}

void solve();

Int W, H;
vector<vector<bool> > M(51, vector<bool>(51, false));

void input() {
  while (true) {
    cin >> W >> H;
    if (W == 0 && H == 0) return;
    bool b;
    loop(h,0,H) {
      loop(w,0,W) {
        cin >> b;
        if (b) M.at(w).at(h) = true;
      }
    }
    solve();
  }
}

void dfs(Int h, Int w) {
  M.at(w).at(h) = false;
  for (int x=-1; x<=1; x++) {
    for (int y=-1; y<=1; y++) {
      if (x == 0 && y == 0) continue;
      Int x1 = w + x, y1 = h + y;
      if (x1 < 0 || W <= x1) continue;
      if (y1 < 0 || H <= y1) continue;
      if (!M.at(x1).at(y1)) continue;
      dfs(y1, x1);
    }
  }
}

void solve() {
  Int count = 0;
  loop(h,0,H) {
    loop(w,0,W) {
      bool b = M.at(w).at(h);
      if (b) {
        count++;
        dfs(h, w);
      }
    }
  }
  cout << count << endl;
}

int main() {
  input();
  return 0;
}