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> 

#define int long long
#define double long double

#define REP(i, b) for(int i = 0; i < (b); i++)
#define REPS(i, b) for(int i = 1; i <= (b); i++)
#define ALL(v) (v).begin(), (v).end()

#define fi first
#define se second
#define pb push_back
#define mp make_pair

using namespace std;

using pi = pair<int, int>;
using vi = vector<int>;
using vd = vector<double>;
using vs = vector<string>;
using vb = vector<bool>;
using vpi = vector<pi>;
using vvi = vector<vi>;
using vvb = vector<vb>;

const int INF = 1e16;
const int MOD = 1e9+7;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }

int w, h;
int d[] = {-1, 0, 1};

void dfs(vvi &c, int y, int x)
{
    c[y][x] = 0;
    REP(i, 3)
    {
        REP(j, 3)
        {
            int ny = y + d[i];
            int nx = x + d[j];
            if(0 <= ny && ny < h && 0 <= nx && nx < w && c[ny][nx] == 1) dfs(c, ny, nx);
        }
    }
}

signed main()
{
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    while(true)
    {
        int ans = 0;
        cin >> w >> h;
        if(w == 0 && h == 0) break;
        vvi c(h, vi(w));
        REP(i, h) REP(j, w) cin >> c[i][j];
        REP(i, h)
        {
            REP(j, w)
            {
                if(c[i][j] == 1)
                {
                    ans++;
                    dfs(c, i, j);
                }
            }
        }
        cout << ans << endl;
    }
}

C++: /************************************
 * ???????????¢?´¢??§??¶?????°?????°??????????????°?????? *
 ************************************/

#include <iostream>
#include <queue>
#include <map>

#define LAND '1'  //??? char???
#define SEA  '0'   //??? char???

using namespace std;

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

/*8??????*/
int dx[] = {1,1,0,-1,-1,-1, 0, 1};
int dy[] = {0,1,1, 1, 0,-1,-1,-1};

bool input(vector< vector<char> > &m);
void delete_island(vector< vector< char > > &m, int x, int y);
void output(vector< vector< char> > m);


int main(){
  int w, h;
    
  while(cin >> w >> h, w && h){
    vector< vector< char > > m(h+2, vector<char>(w+2));
    input(m);
    
    int island = 0;
    for(int y = 0; y < m.size(); y++){
      for(int x = 0; x < m[y].size(); x++){
	if(m[y][x] == LAND){
	  delete_island(m,x,y);
	  island++;
	}
      }
    }
    cout << island << endl;
  }
}


bool input(vector< vector<char> > &m){
  for(int y = 0; y < m.size(); y++){
    for(int x = 0; x < m[y].size(); x++){
      if(y == 0 || x == 0 ||
	 y == m.size()-1 || x == m[y].size()-1){
	m[y][x] = SEA;
      }else{
	if(!(cin >> m[y][x])) return false;
      }
    }
  }
  return true;
}


 void delete_island(vector< vector< char > > &m, int x, int y){
   queue< pair< int, int > > q;
   q.push(make_pair(x,y));

   while(!(q.empty())){
     pair<int, int> cur = q.front();
     q.pop();
     if(m[cur.second][cur.first] == LAND){
       m[cur.second][cur.first] = SEA;
       for(int i = 0; i < sizeof(dx)/sizeof(int); i++){
	 q.push(make_pair(cur.first+dx[i],cur.second+dy[i]));
       }
     }
   }
}

void output(vector< vector< char> > m){
  for(auto y : m){
    for(auto x: y){
      cout << x << " ";
    }
    cout << endl;
  }
  cout << endl;
}

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

int main() {
  int w, h;
  while(cin >> w >> h, w || h) {
    set<pair<int, int> > blacks;
    for(int y = 0; y < h; ++y) for(int x = 0; x < w; ++x) {
      int d;
      cin >> d;
      if(d) blacks.insert(make_pair(y, x));
    }
    function<void(int, int)> countIslands = [&](int y, int x) {
      if(blacks.count(make_pair(y, x))) {
        blacks.erase(make_pair(y, x));
        int dy[] = {0, 1, 0, -1, 1, 1, -1, -1};
        int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
        for(int i = 0; i < 8; ++i) countIslands(y + dy[i], x + dx[i]);
      }
    };
    int ans = 0;
    while(!blacks.empty()) {
      countIslands((*begin(blacks)).first, (*begin(blacks)).second);
      ++ans;
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #include<iostream>
using namespace std;
void dfs(int,int);
int box[52][52];
int main(){
  int w,h,i,I,a;
  while(1){
    a=0;
    cin>>w>>h;
    if(w==0&&h==0) break;
    for(i=0;i<=h+1;i++){
      for(I=0;I<=w+1;I++){
	box[i][I]==0;
      }
    }
    for(i=1;i<=h;i++){
      for(I=1;I<=w;I++){
	cin>>box[i][I];
      }
    }
    for(i=1;i<=h;i++){
      for(I=1;I<=w;I++){
	if(box[i][I]==1){
	  dfs(i,I);
	  a++;
	}
      }
    }
    cout<<a<<endl;
  }
  return 0;
}
  void dfs(int i,int I){
  if(box[i][I]==0) return;
  box[i][I]=0;
  dfs(i,I+1);
  dfs(i+1,I+1);
  dfs(i+1,I);
  dfs(i+1,I-1);
  dfs(i,I-1);
  dfs(i-1,I-1);
  dfs(i-1,I);
  dfs(i-1,I+1);
  }