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;
#define ll long long

bool isprime(int n){
    double rootn = sqrt(n);
    if (n < 2){
        return false;
    }
    else if (n == 2){
        return true;
    }
    else if (n % 2 == 0){
        return false;
    }
    else{
        for(int i = 3; i <= rootn; i += 2){
            if(n % i == 0){
                return false;
            }
        }
        return true;
    }
}

// 空のベクトルを二つ渡す。N (>=2) 以下の素数を primes に順番に入れる。
void prime_vectors(int N, vector<int>& primes, vector<bool>& is_prime){
    primes = {};
    is_prime = {};
    for(int i=0; i<=N; i++){
        is_prime.push_back(true);
    }

    primes.push_back(2);
    for(int j=4; j<=N; j+=2){
        is_prime[j] = false;
    }

    int i;
    for(i=3; i*i<=N; i+=2){
        if(!is_prime[i]) continue;
        primes.push_back(i);
        for(int j=2*i; j<=N; j+=i){
            is_prime[j] = false;
        }
    }

    for(; i<=N; i+=2){
        if(is_prime[i]){
            primes.push_back(i);
        }
    }
}

signed main(){
    // cout << fixed << setprecision(10) << flush;

    int w, h;
    cin >> w >> h;
    vector<int> n_cc;
    while(w != 0 && h != 0){
        vector<vector<int>> c(h+2, vector<int>(w+2, 0));
        for(int i=1; i<=h; i++){
            for(int j=1; j<=w; j++){
                cin >> c[i][j];
            }
        }

        int visited[h+2][w+2] = {0};
        stack<pair<int, int>> stk;
        int cc = 0;
        for(int i=1; i<=h; i++){
            for(int j=1; j<=w; j++){
                if(c[i][j] == 0 || visited[i][j] == 1) continue;
                visited[i][j] = 1;
                stk.push(make_pair(i, j));
                while(!stk.empty()){
                    int i0 = stk.top().first, j0 = stk.top().second;
                    stk.pop();
                    for(int id=-1; id<=1; id++){
                        for(int jd=-1; jd<=1; jd++){
                            if(c[i0+id][j0+jd] == 1 && visited[i0+id][j0+jd] == 0){
                                visited[i0+id][j0+jd] = 1;
                                stk.push(make_pair(i0+id, j0+jd));
                            }
                        }
                    }
                }

                cc++;
            }
        }
        n_cc.push_back(cc);

        cin >> w >> h;
    }

    for(int i=0; i<n_cc.size(); i++){
        cout << n_cc[i] << endl;
    }

    return 0;
}

C++: #include <iostream>
#include <queue>
using namespace std;
struct Point{int x,y;};
int main(){
  int w,h,p[60][60]={},v[60][60]={},i,j,k,o;
  queue <Point> q;
  Point n,b;
  cin >> w >> h;
  while(w!=0){
    for(j=0;j<h;j++){
      for(i=0;i<w;i++){
	cin >> p[i][j];
	v[i][j]=0;
      }
    }
    o=0;
    for(j=0;j<h;j++){
      for(i=0;i<w;i++){
	if(v[i][j]==0&&p[i][j]==1){
	  o++;
	  n.x=i;n.y=j;
	  q.push(n);
	  while(!q.empty()){
	    n=q.front();
	    q.pop();
	    v[n.x][n.y]=1;
	    if(n.x+1<w&&v[n.x+1][n.y]==0&&p[n.x+1][n.y]==1) {
	      b.x=n.x+1;b.y=n.y;
	      q.push(b);
	    }
	    if(n.y+1<h&&v[n.x][n.y+1]==0&&p[n.x][n.y+1]==1) {
	      b.x=n.x;b.y=n.y+1;
	      q.push(b);
	    }
	    if(n.x-1>=0&&v[n.x-1][n.y]==0&&p[n.x-1][n.y]==1) {
	      b.x=n.x-1;b.y=n.y;
	      q.push(b);
	    }
	    if(n.y-1>=0&&v[n.x][n.y-1]==0&&p[n.x][n.y-1]==1) {
	      b.x=n.x;b.y=n.y-1;
	      q.push(b);
	    }
	    if(n.x+1<w&&n.y+1<h&&v[n.x+1][n.y+1]==0&&p[n.x+1][n.y+1]==1) {
	      b.x=n.x+1;b.y=n.y+1;
	      q.push(b);
	    }
	    if(n.x-1>=0&&n.y-1>=0&&v[n.x-1][n.y-1]==0&&p[n.x-1][n.y-1]==1) {
	      b.x=n.x-1;b.y=n.y-1;
	      q.push(b);
	    }
	    if(n.x+1<w&&n.y-1>=0&&v[n.x+1][n.y-1]==0&&p[n.x+1][n.y-1]==1) {
	      b.x=n.x+1;b.y=n.y-1;
	      q.push(b);
	    }
	    if(n.x-1>=0&&n.y+1<h&&v[n.x-1][n.y+1]==0&&p[n.x-1][n.y+1]==1) {
	      b.x=n.x-1;b.y=n.y+1;
	      q.push(b);
	    }
	  }
	}
      }
    }
    cout << o << endl;
    cin >> w >> h;
  }
  return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
int w, h, isl, v;
int a[2501];
deque<int> Q;
int main()
{
	while(cin >> w >> h && w>0)
	{
		for(int i=1; i<=w*h; i++)
		{
			cin >> a[i];
		}
		isl=0;
		for(int i=1; i<=w*h; i++)
		{
			if(a[i]==1)
			{
				isl++;
				Q.clear();
				Q.push_back(i);
				while(!Q.empty())
				{
					v=Q.front();
					Q.pop_front();
					if(v>w)
					{
						if(a[v-w]==1)
						{
							a[v-w]=0;
							Q.push_back(v-w);
						}
						if(v%w!=1)
						{
							if(a[v-w-1]==1)
							{
								a[v-w-1]=0;
								Q.push_back(v-w-1);
							}
						}
					}
					if(v%w!=1)
					{
						if(a[v-1]==1)
						{
							a[v-1]=0;
							Q.push_back(v-1);
						}
					}
					if(v%w!=0)
					{
						if(v>w)
						{
							if(a[v-w+1]==1)
							{
								a[v-w+1]=0;
								Q.push_back(v-w+1);
							}
						}
						if(a[v+1]==1)
						{
							a[v+1]=0;
							Q.push_back(v+1);
						}
						if(v+w<w*h)
						{
							if(a[v+w+1]==1)
							{
								a[v+w+1]=0;
								Q.push_back(v+w+1);
							}
						}
					}
					if(v+w<=w*h)
					{
						if(v%w!=1)
						{
							if(a[v+w-1]==1)
							{
								a[v+w-1]=0;
								Q.push_back(v+w-1);
							}
						}
						if(a[v+w]==1)
						{
							a[v+w]=0;
							Q.push_back(v+w);
						}
					}
				}
			}
		}
		cout << isl << endl;
	}
	return 0;
}