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>
#define R 1
#define U 0
using namespace std;
int w,h;
int c[60][60];

void rec(int x,int y){
  if( x<0 || x>=h ) return;
  if( y<0 || y>=w ) return;
  if( c[x][y]==U )  return;

  c[x][y]=U;
  for( int i=-1;i<=1;i++ ){
    for( int j=-1;j<=1;j++ ){
      if( i==j && i==0 ) continue;
      rec( x+i,y+j );
    }
  }
}

int main(){
  while( cin>>w>>h && (w|h) ){
    for( int i=0;i<h;i++ )
      for( int j=0;j<w;j++ )
	cin >> c[i][j];
    int ans=0;
    for( int i=0;i<h;i++ ){
      for( int j=0;j<w;j++ ){
	if( c[i][j]==R ){
	  ans++;
	  rec( i,j );
	}
      }
    }
    cout << ans << endl;
  }

  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
typedef pair<ll, P> P3;
typedef pair<P ,P> PP;
constexpr ll MOD = ll(1e9) + 7;
constexpr int IINF = INT_MAX;
constexpr ll LLINF = LLONG_MAX;
constexpr int MAX_N = int(2e5) + 5;
constexpr double EPS = 1e-9;
constexpr int di[] = {0, 1, 0, -1}, dj[] = {1, 0, -1, 0};
#define REP(i, n) for (int i = 0; i < n; i++)
#define REPR(i, n) for (int i = n; i > 0; i--)
#define SORT(v) sort((v).begin(), (v).end())
#define SORTR(v) sort((v).rbegin(), (v).rend())
#define ALL(v) (v).begin(), (v).end()

int h, w, field[55][55];

void dfs(int i, int j){
    field[i][j] = 0;

    for(int di=-1;di<=1;di++){
        for(int dj=-1;dj<=1;dj++){
            int ni = i + di, nj = j + dj;
            if(ni < 0 || ni >= h) continue;
            if(nj < 0 || nj >= w) continue;
            if(field[ni][nj] == 1){
                dfs(ni, nj);
            }
        }
    }
}

int main() {
    while(cin >> w >> h, w){
        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                cin >> field[i][j];
            }
        }
        int ans = 0;
        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                if(field[i][j] == 1){
                    dfs(i,j);
                    ans++;
                }
            }
        }
        cout << ans << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <string>
#include <set>
#include <algorithm>
using namespace std;
int group[55][55];
int parent(int n){
	int i=n/55,j=n%55;
	if(group[i][j]==-1)	return -1;
	return group[i][j]=(group[i][j]==n?group[i][j]:parent(group[i][j]));
}
void merge(int s,int t){
	int si=s/55,sj=s%55;
	s=parent(group[si][sj]);
	int ti=t/55,tj=t%55;
	t=parent(group[ti][tj]);
	group[t/55][t%55]=s;
}
bool isInside(int i,int j,int w,int h){
	if(i<0||h<=i)	return false;
	if(j<0||w<=j)	return false;
	return true;
}
const int dx[]={1,0,-1};
const int dy[]={1,0,-1};
int main(){
	while(true){
		int w,h;	cin>>w>>h;
		if(w==0)	break;
		for(int i=0;i<h;i++)	for(int j=0;j<w;j++)	group[i][j]=-1;
		for(int i=0;i<h;i++)	for(int j=0;j<w;j++){
			int c;	cin>>c;
			if(c==1)	group[i][j]=55*i+j;
		}
		for(int i=0;i<h;i++)	for(int j=0;j<w;j++){
			if(group[i][j]>=0){
				for(int x=0;x<3;x++)	for(int y=0;y<3;y++){
					int ni=i+dy[y],nj=j+dx[x];
					if(!isInside(ni,nj,w,h))	continue;
					if(group[ni][nj]>=0)	merge(55*i+j,55*ni+nj);
				}
			}
		}
		set<int> ret;
		for(int i=0;i<h;i++)	for(int j=0;j<w;j++)	ret.insert(parent(group[i][j]));
		ret.erase(-1);
		cout<<ret.size()<<endl;
	}
	return 0;
}

C++: #include <utility>
#include <iostream>
#include <algorithm>
#include <vector>
#include <cstdio>
using namespace std;
int cnt;
int t[3]={-1,0,1};
    int map[55][55];
void dfs(int h,int w){
    if(map[h][w]==1){
        map[h][w]=0;
        for(int i=0;i<3;i++){for(int j=0;j<3;j++)dfs(h+t[i],w+t[j]);}
       }
}
int main()
{
    int w,h;

    while(cin>>w>>h,w+h){cnt=0;
        for(int i=0;i<55;i++){for(int j=0;j<55;j++)map[i][j]=0;}
        for(int i=0;i<h;i++){for(int j=0;j<w;j++)scanf("%d",&map[i+1][j+1]);}
        for(int i=0;i<53;i++){for(int j=0;j<53;j++){
            if(map[i][j]==1)cnt++;
            dfs(i,j);}}
        cout<<cnt<<endl;}
    return 0;
}