Go: // AOJ 1160: How Many Islands? http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=1160

package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
)

var SEA = 0
var LAND = 1

func nextInt(sc *bufio.Scanner) int {
	sc.Scan()
	v, _ := strconv.Atoi(sc.Text())
	return v
}

func discoverIslands(M, V [][]int, H, W int) int {
	// 島を探す
	queue := list.New()
	islands := 0
	for i := 1; i <= H; i++ {
		for j := 1; j <= W; j++ {
			// 訪問済みの土地ならスキップ
			if V[i][j] == 1 {
				continue
			}

			// 訪問中の土地が海なら訪問済みにしてスキップ
			if M[i][j] == SEA {
				V[i][j] = 1
				continue
			}

			// 未訪問の陸地が見つかったので
			// 島の数を1つ増やし、この陸地から辿れる陸地を訪問していく
			islands++
			queue.PushBack([]int{i, j})

			for queue.Len() > 0 {
				cur := queue.Remove(queue.Front()).([]int)
				h, w := cur[0], cur[1]
				if V[h][w] == 1 {
					continue
				}
				V[h][w] = 1

				// 全方向に未訪問の陸地がないか探索
				for v := -1; v <= 1; v++ {
					for l := -1; l <= 1; l++ {
						dh := h + v
						dw := w + l
						if M[dh][dw] == LAND && V[dh][dw] == 0 {
							queue.PushBack([]int{dh, dw})
						}
					}
				}
				/*
					if M[h-1][w] == LAND {
						queue.PushBack([]int{h - 1, w})
					}
					if M[h-1][w+1] == LAND {
						queue.PushBack([]int{h - 1, w + 1})
					}
					if M[h][w+1] == LAND {
						queue.PushBack([]int{h, w + 1})
					}
					if M[h+1][w+1] == LAND {
						queue.PushBack([]int{h + 1, w + 1})
					}
					if M[h+1][w] == LAND {
						queue.PushBack([]int{h + 1, w})
					}
					if M[h+1][w-1] == LAND {
						queue.PushBack([]int{h + 1, w - 1})
					}
					if M[h][w-1] == LAND {
						queue.PushBack([]int{h, w - 1})
					}
					if M[h-1][w-1] == LAND {
						queue.PushBack([]int{h - 1, w - 1})
					}
				*/
			}
		}
	}
	return islands
}

func main() {
	sc := bufio.NewScanner(os.Stdin)
	sc.Split(bufio.ScanWords)

	for {
		W, H := nextInt(sc), nextInt(sc)

		if W == 0 && H == 0 {
			break
		}
		// Initialize map and visted list
		M := make([][]int, H+2)
		V := make([][]int, H+2)
		for i := 0; i < H+2; i++ {
			M[i] = make([]int, W+2)
			V[i] = make([]int, W+2)
		}
		for i := 1; i <= H; i++ {
			for j := 1; j <= W; j++ {
				M[i][j] = nextInt(sc)
			}
		}

		islands := discoverIslands(M, V, H, W)

		fmt.Println(islands)
	}
}

C++: #include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<cstring>
using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)
#define REP(n) rep(i,n)

const int MAXW = 52;

bool tile[MAXW][MAXW];

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

int solve(int x, int y)
{
    if(!tile[x][y]) return 0;
    tile[x][y] = false;
    REP(8)
        solve(x + dx[i], y + dy[i]);
    return 1;
}
int w,h;
int main()
{
    while(cin >> w >> h && w)
    {
        memset(tile, false, sizeof(tile));

        rep(j,h)rep(i,w) cin >> tile[i+1][j+1] ;

        int ans = 0;
        rep(j,h)rep(i,w)ans += solve(i+1, j+1);
        cout << ans << endl;

    }

    return 0;
}

C++: #include <bits/stdc++.h>
#define debug(x) cerr << #x << ": " << x << '\n';
using namespace std;
using ll = long long;
using P = pair<int, int>;
const int INF = (int)1e9;

int w, h;
int c[51][51];
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){
	c[y][x] = 0;
	for(int i = 0; i < 8; i++){
		int ny = y + dy[i], nx = x + dx[i];
		if(0<=ny and ny<h and 0<=nx and nx<w and c[ny][nx]==1){
			dfs(ny, nx);
		}
	}
}

int solve(){
	int res = 0;
	for(int i = 0; i < h; i++){
		for(int j = 0; j < w; j++){
			if(c[i][j] == 1){
				dfs(i, j);
				res++;
			}
		}
	}

	return res;
}

int main(void){
	while(scanf("%d%d", &w, &h) != EOF){
		if(w == 0 and h == 0) break;
		for(int i = 0; i < h; i++){
			for(int j = 0; j < w; j++){
				scanf("%d", &(c[i][j]));
			}
		}
		printf("%d\n", solve());
	}

	return 0;
}

C++: #include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <stack>
#include <deque>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <tuple>
#include <numeric>
#include <string>
#include <bitset>
#include <functional>

using ld = long double;
using vld = std::vector<ld>;
using vvld = std::vector<vld>;
using vvvld = std::vector<vvld>;
using ll = long long;
using vll = std::vector<ll>;
using vvll = std::vector<vll>;
using vvvll = std::vector<vvll>;
using pll = std::pair<ll, ll>;
using vpll = std::vector<pll>;
using str = std::string;
using vstr = std::vector<str>;

template<typename T> bool chmin(T a, T &b) { return a < b ? b = a, true : false; }
template<typename T> bool chmax(T a, T &b) { return a > b ? b = a, true : false; }

constexpr ld PI = 3.141592653589793L;
constexpr ld EPS = std::numeric_limits<ld>::epsilon();

ll gcd(ll n, ll m) { return m ? gcd(m, n % m) : n; }
ll lcm(ll n, ll m) { return n / gcd(n, m) * m; }
bool is_prime(ll n) {
    if (n == 1) return false;
    for (ll i = 2; i * i <= n; i++)
        if (n % i == 0) return false;
    return true;
}

/*------------------------------------------------------------------------*/

void solve();

int main() {
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    std::cout << std::setprecision(15);

    solve();
}
void solve() {
    const vll dy = { -1, -1, -1, 0, 1, 1, 1, 0 }, dx = { -1, 0, 1, 1, 1, 0, -1, -1 };

    while (true) {
        ll w, h; std::cin >> w >> h;

        if (w == 0 && h == 0) break;

        vvll g(h, vll(w));
        for (ll i = 0; i < h; i++) for (ll j = 0; j < w; j++)
            std::cin >> g[i][j];

        vvll flg(h, vll(w, 0));

        auto bfs = [&](ll sy, ll sx) -> void {
            flg[sy][sx]++;
            std::queue<pll> que; que.push({ sy, sx });

            while (!que.empty()) {
                pll p = que.front(); que.pop();
                ll cy = p.first, cx = p.second;
                for (ll i = 0; i < 8; i++) {
                    ll ny = cy + dy[i], nx = cx + dx[i];
                    if (0 <= ny && ny < h && 0 <= nx && nx < w
                        && g[ny][nx] && !flg[ny][nx]) {
                        flg[ny][nx]++;
                        que.push({ ny, nx });
                    }
                }
            }
        };

        ll ans = 0;
        for (ll i = 0; i < h; i++) for (ll j = 0; j < w; j++)
            if (g[i][j] && !flg[i][j]) {
                ans++; bfs(i, j);
            }

        std::cout << ans << '\n';
    }
}

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

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

// 現在地(x,y)
void dfs(int x, int y){
    // 今いるところを-1に置き換える
    field[y][x] = -1;

    // 移動する8方向をループ
    for(int dx = -1 ; dx <= 1 ; dx++ ){
        for(int dy = -1 ; dy <= 1 ; dy++ ){
            // x方向にdx, y方向にdy, 移動した場所を(mx,my)とする
            int mx = x + dx;
            int my = y + dy;
            // 範囲外に出たときは次の処理へ
            if( mx < 0 || my < 0 || mx >= w || my >= h ) continue;
            // 陸地だったら再帰呼び出し
            if( field[my][mx] == 1 ){
                dfs( mx , my );
            }
        }
    }
}

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 ){ // 陸地があったら再帰関数を呼び出す
                    dfs( x , y );
                    ans++;
                }
            }
        }
        cout << ans << endl;
    }
}