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;
#define rep(begin, i, end) for (int i = begin; i < (int)(end); i++)
#define all(v) v.begin(), v.end()
const int MOD = 1000000007;

int w, h;
vector<int> ans;

void dfs(int x, int y, vector<vector<int>> &m, vector<vector<bool>> &seen);

int main()
{
    while (true)
    {
        cin >> w >> h;
        // 終了条件
        if ((w == 0) && (h == 0))
        {
            break;
        }
        vector<vector<int>> m(52, vector<int>(52, 0));
        vector<vector<bool>> seen(52, vector<bool>(52, false));
        // データの受け取り
        rep(1, i, h + 1)
        {
            rep(1, j, w + 1)
            {
                cin >> m.at(i).at(j);
            }
        }
        int count = 0;
        //すべての点で探索
        rep(1, i, h + 1)
        {
            rep(1, j, w + 1)
            {
                // 探索済か海のマスならとばす
                if (seen.at(i).at(j) || (m.at(i).at(j) == 0))
                {
                    continue;
                }
                // dfsによる塗りつぶし
                dfs(i, j, m, seen);
                count++;
            }
        }
        ans.push_back(count);
    }
    for (auto a : ans)
    {
        cout << a << endl;
    }
}

void dfs(int x, int y, vector<vector<int>> &m, vector<vector<bool>> &seen)
{
    // 探索済か海のマスなら探索終了
    if (seen.at(x).at(y) || (m.at(x).at(y) == 0))
    {
        return;
    }
    // 探索済の印をつける
    seen.at(x).at(y) = true;
    rep(-1, dx, 2)
    {
        rep(-1, dy, 2)
        {
            dfs(x + dx, y + dy, m, seen);
        }
    }
    return;
}

C++: #include <bits/stdc++.h>
#include <unistd.h>

using namespace std;

#define DEBUG(x) cerr<<#x<<": "<<x<<endl;
#define DEBUG_VEC(v) cerr<<#v<<":";for(int i=0;i<v.size();i++) cerr<<" "<<v[i]; cerr<<endl
#define DEBUG_MAT(v) cerr<<#v<<endl;for(int i=0;i<v.size();i++){for(int j=0;j<v[i].size();j++) {cerr<<v[i][j]<<" ";}cerr<<endl;}


typedef long long ll;
#define vi vector<int>
#define vl vector<ll>
#define vii vector< vector<int> >
#define vll vector< vector<ll> >
#define vs vector<string>
#define pii pair<int,int>
#define pis pair<int,string>
#define psi pair<string,int>
#define pll pair<ll,ll>
template<class S, class T> pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first + t.first, s.second + t.second); }
template<class S, class T> pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template<class S, class T> ostream& operator<<(ostream& os, pair<S, T> p) { os << "(" << p.first << ", " << p.second << ")"; return os; }
#define X first
#define Y second
#define rep(i,n) for(int i=0;i<(n);i++)
#define rep1(i,n) for(int i=1;i<=(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define rrep1(i,n) for(int i=(n);i>0;i--)
#define REP(i,a,b) for(int i=a;i<b;i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(),c.end()
template<class T> bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T> bool chmin(T &a, const T &b) { if (a>b) { a = b; return 1; } return 0; }
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const ll MOD = 1000000007;
//const ll MOD = 998244353;
const double pi = 3.14159265358979323846;
#define Sp(p) cout<<setprecision(15)<< fixed<<p<<endl;
int dx[4] = { 1,0, -1,0 }, dy[4] = { 0,1,0,-1 };
int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
#define fio() cin.tie(0); ios::sync_with_stdio(false);
//#define mp make_pair

int w, h;

void dfs(vii &a, int ii, int jj, int d) {
  a[ii][jj] = d;
  rep (k, 8) {
    if (in(ii + dx2[k], 0, h) && in(jj + dy2[k], 0, w) && a[ii + dx2[k]][jj + dy2[k]] == -1) {
      dfs(a, ii + dx2[k], jj + dy2[k], d);
    }
  }
}

int main() {
  while (true) {
    cin >> w >> h;
    if (h == 0) return 0;
    vii a(h, vi(w));
    rep (i, h) {
      rep (j, w) {
        cin >> a[i][j];
        a[i][j] *= -1;
      }
    }

    int ans = 0;
    rep (i, h) {
      rep (j, w) {
        if (a[i][j] == -1) {
          ans++;
          dfs(a, i, j, ans);
        }
      }
    }

    cout << ans << endl;
    
  }
}

C++: #include <iostream>
using namespace std;

int dx[] = { 0,  1, 1, 1, 0, -1, -1, -1};
int dy[] = {-1, -1, 0, 1, 1,  1,  0, -1};

int map[51][51];
int w, h;

//void printmap() {
//	for (int i = 0 ; i < h; i++) {
//		for (int j = 0; j < w; j++)
//			cout << map[i][j] << " ";
//		cout << endl;
//	}
//}

void oneIsland(int x, int y) {
	if (x < 0 || w <= x) return;
	if (y < 0 || w <= y) return;
	if (map[y][x] == 0) return;
	map[y][x] = 0;
	for (int i = 0; i < 8; i++) {
		int nextX = x + dx[i];
		int nextY = y + dy[i];
		oneIsland(nextX, nextY);
	}
}

int main() {
	while (1) {
		cin >> w >> h;
		if (w == 0 && h == 0) break;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				cin >> map[i][j];
			}
		}
		
		int count = 0;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if (map[i][j] == 1) {
					oneIsland(j, i);
					//printmap();
					count++;
				}
			}
		}
		cout << count <<endl;
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const ll INF = 1LL << 60;
const ll MOD = 1000000007;

int W, H;
vector<vector<int>> field;

void dfs(int h, int w) {
    field[h][w] = 0;
    
    for (int dh = -1; dh <= 1; dh++) {
        for (int dw = -1; dw <= 1; dw++) {
            int nh = h + dh;
            int nw = w + dw;
            if (nh < 0 || nh >= H || nw < 0 || nw >= W) continue;
            if (field[nh][nw] == 0) continue;

            dfs(nh, nw);
        }
    }
}

int main() {
    while(cin >> W >> H) {
        if (H == 0 && W == 0) break;
        field.assign(H, vector<int>(W, 0));
        for (int h = 0; h < H; h++) {
            for (int w = 0; w < W; w++) {
                cin >> field[h][w];
            }
        }

        int cnt = 0;
        for (int h = 0; h < H; h++) {
            for (int w = 0; w < W; w++) {
                if (field[h][w] == 0) continue;
                dfs(h, w);
                cnt++;
            }
        }

        cout << cnt << endl;
    }
    return 0;
}