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 <algorithm>

using namespace std;

int w, h;
int field[51][51];
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

void dfs(int x, int y)
{
    field[y][x] = -1;

    for (int i = 0; i < 4; i++)
    {
        int nx = x + dx[i];
        int ny = y + dy[i];

        if (nx < 0 || ny < 0 || nx >= w || ny >= h)
            continue;

        if (field[ny][nx] == 1)
            dfs(nx, ny);
    }
}

int main()
{
    while (cin >> w >> h, w || h)
    {
        for (int y = 0; y < h; y++)
        {
            for (int x = 0; x < w; x++)
            {
                cin >> field[y][x];
            }
        }

        int ans = 0;

        for (int y = 0; y < h; y++)
        {
            for (int x = 0; x < w; x++)
            {
                if (field[y][x] == 1)
                {
                    dfs(x, y);
                    ans++;
                }
            }
        }

        cout << ans << endl;
    }

    return 0;
}

C++: #include "bits/stdc++.h"
#include<unordered_map>
#include<unordered_set>
#pragma warning(disable:4996)
using namespace std;
using ld = long double;
template<class T>
using Table = vector<vector<T>>;

//
int dx8[8] = { -1,-1,-1, 0, 1, 1, 1, 0 };
int dy8[8] = { -1, 0, 1, 1, 1, 0,-1,-1 };
//6:28
vector<vector<int>>as;
void check(int y, int x) {
	for (int i = 0; i < 8; ++i) {
		int nx = x + dx8[i];
		int ny = y + dy8[i];
		if (as[ny][nx]) {
			as[ny][nx] = 0;
			check(ny, nx);
		}
	}
}
int main() {
	while (1) {
		as.clear();
		int w, h; cin >> w >> h;
		if (!w)break;
		as.resize(h+2);
		for (int i = 0; i <= h+1; ++i) {
			as[i].emplace_back(0);
			if (i != 0 && i != h + 1) {
				for (int j = 0; j < w; ++j) {
					int c; cin >> c;
					as[i ].emplace_back(c);
				}
			}
			else {
				for (int j = 0; j < w; ++j) {
					as[i].emplace_back(0);
				}
			}
			
			as[i].emplace_back(0);
		}
		int ans = 0;
		for (int i = 1; i <= h; ++i) {
			for (int j = 1; j <= w; ++j) {
				if (as[i][j]) {
					ans++;
					check(i, j);
				}
			}
		}
		cout << ans << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <list>
#include <set>
#include <string>
#include <cmath>
#include <algorithm>
#include <map>

using namespace std;
using ll=long long;
using vi=vector<int>;
using vll=vector<ll>;
using pii=pair<int,int>;
using vs=vector<string>;
using vvi=vector<vi>;
using vpii=vector<pii>;
using si=set<int>;

#define REP(i,a) for(int i=0;i<a;i++)
#define FOR(i,a,b) for(int i=a;i<b;i++)
#define rREP(i,a) for(int i=(a)-1;i>=0;i--)
#define rFOR(i,a,b) for(int i=(a)-1;i>=(b);i--)
#define out(S) cout<<(S)<<endl;
#define beginend(v) (v).begin(),(v).end()
#define IfOut(condition,text) if(condition){out(text);return 0;}
#define IfOutElse(condition,if_text,else_text) if(condition){out(if_text);return 0;}else{out(else_text);return 0;}
#define mod(s) ((s)%(ll)(1e9+7))
ll modpow(ll i, ll j) { ll tmp = 1; while (j) { if (j % 2)tmp = mod(tmp*i); i = mod(i*i); j /= 2; }return tmp; }
#define divmod(a,b) (mod(a*modpow((ll)b,(ll)(1e9+5))))
#define pb(i) push_back(i)
#define fst first
#define snd second
#define Foreach(item,collection) for(auto item:collection)
#define INF (int)1e10
#define removeAll(vec,deleg) auto itr=remove_if(beginend(vec),deleg);vec.erase(itr,vec.end());
void removeAt(string& s, int index) { s.erase(index, 1); }
template<typename T> void removeAt(vector<T>& v, int index) { v.erase(v.begin() + index); }
ll manhattanDistance(ll x1, ll y1, ll x2, ll y2) { return (abs(x2 - x1) + abs(y2 - y1)); }
vector<ll> sieveOfEratosthenes(int max) {ll prime;double sqrtmax = sqrt(max);vector<ll> primeVec, searchVec;FOR(i, 2, max + 1) searchVec.push_back(i);do{prime = searchVec[0];primeVec.push_back(prime);auto itr = remove_if(beginend(searchVec), [=](ll x)->bool {return x%prime == 0; });searchVec.erase(itr, searchVec.end());} while (prime < sqrtmax);primeVec.reserve(primeVec.size() + searchVec.size());primeVec.insert(primeVec.end(), beginend(searchVec));return primeVec;}
ll sum(vi v) {ll sum=0;Foreach(i,v){sum+=i;}return sum;}
#define ShowAll(v) Foreach(i,v) out(i);
bool isInnerIndex(int kx,int ky,int mx,int my){ return (kx>=0&&kx<mx&&ky>=0&&ky<my); }

int x,y;
vvi box;
int dx[]{0,1,0,-1,1,1,-1,-1};
int dy[]{1,0,-1,0,-1,1,-1,1};
ll s=0;
void dfs(int px,int py){
    box[py][px]=2;
    REP(i,8){
        int nx=px+dx[i];
        int ny=py+dy[i];
        if(isInnerIndex(nx,ny,x,y)){
            if(box[ny][nx]==1)dfs(nx,ny);
        }
    }
    return;
}

int main(){
    vi ans;
    while (cin>>x>>y,(x||y))
    {
        box.clear();
        box.resize(y);
        REP(i,y) REP(n,x) {
            int c;
            cin>>c;
            box[i].pb(c);
        }
        ll s=0;
        REP(i,y)REP(n,x){
            if(box[i][n]==1) {dfs(n,i);s++;}
        }
        ans.pb(s);
    }
    
    ShowAll(ans);
    return 0;
}

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

int H,W;
int c[55][55];
vector<vector<int > > s(55,vector<int>(55));
bool seen[55][55];
int dx[] = {1, -1, 0, 0, 1, -1, 1, -1};
int dy[] = {0, 0, 1, -1, 1, -1, -1, 1};
void dfs(int y,int x,int a){
  if(x<0||W<=x||y<0||H<=y||c[y][x]==0){return;}
  if(seen[y][x]){return;}
  seen[y][x]=true;s[y][x]=a;
  for(int i=0;i<8;i++){
    dfs(y+dy[i],x+dx[i],a);
  }
}

int main() {
 while(cin>>W>>H){
  if(W==0&&H==0){return 0;}
 // vector<vector<int > > s(55,vector<int>(55));
  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      s[i][j]=0;
    }
  }
  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      cin>>c[i][j];
    }
  }
  for(int i=0;i<55;i++){
    for(int j=0;j<55;j++){
      seen[i][j]=false;
    }
  }
  int a=1;
  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      if(c[i][j]){dfs(i,j,a);a++;}
    }
  }
  set<int>k;k.insert(0);
  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      if(s[i][j]){k.insert(s[i][j]);}
    }
  }
  cout<<k.size()-1<<endl;
 }
  return 0;
}