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<bits/stdc++.h>
using namespace std;
using ll = long long;
using VI = vector<ll>;
using VV = vector<VI>;
using VS = vector<string>;

// tourist set
template <typename A, typename B>
string to_string(pair<A, B> p);

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);

string to_string(const string& s) {
  return '"' + s + '"';
}

string to_string(const char* s) {
  return to_string((string) s);
}

string to_string(bool b) {
  return (b ? "true" : "false");
}

string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (int i = 0; i < static_cast<int>(v.size()); i++) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}

template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}

template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto &x : v) {
    if (!first) {
      res += ", ";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}

template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}

template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ")";
}

template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + ", " + to_string(get<1>(p)) + ", " + to_string(get<2>(p)) + ", " + to_string(get<3>(p)) + ")";
}

void debug_out() { cerr << '\n'; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}

#ifdef LOCAL
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
// tourist set 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 (b<a) { a=b; return 1; } return 0; }

#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i,b) FOR(i, 0, b)
#define ALL(v) (v).begin(), (v).end()
#define p(s) cout<<(s)<<'\n'
#define p2(s, t) cout << (s) << " " << (t) << '\n'
#define br() p("")
#define pn(s) cout << (#s) << " " << (s) << '\n'
#define p_yes() p("YES")
#define p_no() p("NO")
#define SZ(x) ((int)(x).size())
#define SORT(A) sort(ALL(A))
#define RSORT(A) sort(ALL(A), greater<ll>())

void no(){p_no(); exit(0);}
void yes(){p_yes(); exit(0);}

const ll mod = 1e9 + 7;
const ll inf = 1e18;
const double PI = acos(-1);


using PII = pair<ll, ll>;
#define MP make_pair
int dx[8] = {-1, 0, 1,  0, -1, 1, -1,  1};
int dy[8] = { 0, 1, 0, -1, -1, 1,  1, -1};


int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    // input
    ll w,h;

    while(cin>>w>>h){
      if(w==0) return 0;

      VV G(h);
      rep(i, h){
        rep(j, w){
          ll a; cin >> a;
          G[i].push_back(a);
        }
      }

      ll cnt = 0;
      rep(i, h){
        rep(j, w){
          if(G[i][j]==1){
            G[i][j]=0;
            cnt++;
            // bfs
            queue<PII> que;
            que.push(MP(i,j));
            while(!que.empty()){
              auto pa = que.front(); que.pop();
              rep(k, 8){
                ll ty = pa.first + dy[k];
                ll tx = pa.second+ dx[k];
                if(0<=ty && ty<h && 0<=tx && tx<w && G[ty][tx]==1){
                  G[ty][tx] = 0;
                  que.push(MP(ty, tx));
                }
              }
            }
          }
        }
      }
      p(cnt);
    }
    
    return 0;
}

C++: #include <iostream>
#include <algorithm>

using namespace std;

struct Point{
	int x, y;
};

const Point DIR[] = {{1,0},{1,1},{0,1},{-1,1},{-1,0},{-1,-1},{0,-1},{1,-1}};
//ななめ移動ができる

int w,h;
int map[50][50];//1:陸 0:海
bool visited[50][50];

bool inField(Point pos){
	return 0<=pos.x && pos.x<w && 0<=pos.y && pos.y<h;
}

//同じ島のvisitedを埋める
void dfs(Point pos){
	visited[pos.y][pos.x] = true;
	for(int i=0;i<8;i++){
		Point next={pos.x + DIR[i].x, pos.y + DIR[i].y};
		if(inField(next)==true){
			if(visited[next.y][next.x] == false && map[next.y][next.x] == 1){
				//未訪問かつ、陸
				dfs(next);
			}
		}
	}
}

int main(){
	while(true){
		cin >> w >> h;
		if(w==0){
			break;
		}
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				cin >> map[i][j];
				visited[i][j] = false;
			}
		}
		int cnt = 0;//島の数
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				if(visited[i][j] == false && map[i][j] == 1){
					Point pos = {j,i};
					dfs(pos);
					cnt++;
				}
			}
		}
		cout << cnt << endl;
	}
	return 0;
}

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

const int dx2[] = {1,1,1,0,0,0,-1,-1,-1};
const int dy2[] = {1,0,-1,1,0,-1,1,0,-1};

void go(vector<vector<int> > &F,int h,int w){
    if(F[h][w]==0) return;
    F[h][w] = 0;
    for(int i=0;i<9;i++){
        go(F,h+dy2[i],w+dx2[i]);
    }
}
int main(){
    while(true){
        int w,h;
        cin >> w >> h;
        if(w==0) break;
        vector<vector<int> > F(h+2,vector<int>(w+2,0));
        for(int i=1;i<=h;i++){
            for(int j=1;j<=w;j++){
                cin >> F[i][j];
            }
        }
        int c=0;
        for(int i=0;i<h+2;i++){
            for(int j=0;j<w+2;j++){
                if(F[i][j] == 1){
                    go(F,i,j);
                    c++;
                }
            }
        }
        cout << c << endl;
    }
    return 0;
}