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 <vector>

using namespace std;

int w = 0;
int h = 0;
vector<vector<int>> island;
vector<vector<bool>> reached;

void go(int x_pos, int y_pos);

int main()
{
    while(1){
        cin >> w >> h;
        if(w == 0) break;
        
        island.resize(h);        
        for(int i = 0; i < h; i++){
            island[i].resize(w);
        }
        for(int i = 0; i < h; i++){
            for(int j = 0; j < w; j++){
                cin >> island[i][j];
            }
        }

        reached.resize(h);
        for(int i = 0; i < h; i++){
            reached[i].resize(w);
        }
        for(int i = 0; i < h; i++){
            for(int j = 0; j < w; j++){
                reached[i][j] = false;
            }
        }


        int count = 0;
        for(int i = 0; i < h; i++){
            for(int j = 0; j < w; j++){
                if(island[i][j] == 1 && !reached[i][j]){
                    count++;
                    go(j, i);
                }
            }
        }
        
        cout << count << endl;
        
    }
    return 0;
}

void go(int x_pos, int y_pos)
{
    reached[y_pos][x_pos] = true;
    for(int dx = -1; dx <= 1; dx++){
        for(int dy = -1; dy <= 1; dy++){
            if(x_pos + dx >= 0 && x_pos + dx < w && y_pos + dy >= 0 && y_pos + dy < h){
                if(island[y_pos+dy][x_pos+dx] == 1 && !reached[y_pos+dy][x_pos+dx]){
                    go(x_pos+dx, y_pos+dy);
                }
            }
        }
    }
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <cmath>
#include <algorithm>
#include <cstdlib>
#include <ctime>
#include <cstdio>
#include <functional>
#include <set>
#include <sstream>
#include <map>
#include <queue>

using namespace std;
 
const double eps=1e-10;

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

int main()
{

	int w,h;
	while(cin>>w>>h,w){
		vector< vector<int> > table(h,vector<int>(w));
		int res=0;
		for(int y=0;y<h;y++){
			for(int x=0;x<w;x++) cin>>table[y][x];
		}

		queue< pair<int,int> > q;

		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){

				if(table[i][j]==0) continue;

				res++;
				q.push(make_pair(i,j));

				while(!q.empty()){
					pair<int,int> p=q.front();
					q.pop();
					int y=p.first,x=p.second;

//					cout<<y<<" "<<x<<endl;

					if(table[y][x]==0) continue;

					table[y][x]=0;
					for(int k=0;k<8;k++){
						int nx=x+dx[k],ny=y+dy[k];
						if(0<=nx && nx<w && 0<=ny && ny<h && table[ny][nx]==1) q.push(make_pair(ny,nx));
					}
				}
			}
		}
		cout<<res<<endl;

	}


	return 0;
}

C++: #include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <map>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <bitset>
#include <algorithm>
#include <numeric>
#include <functional>
using namespace std;

#define Rep(b, e, i) for(int i = b; i <= e; i++)
#define Repr(e, b, i) for(int i = e; i >= b; i--)
#define rep(n, i) Rep(0, n-1, i)
#define repr(n, i) Repr(n-1, 0, i)
#define all(v) (v).begin(), (v).end()
#define pb(x) push_back(x)
#define uniq(x) (x).erase(unique(all(x)),(x).end())

typedef long long ll;
typedef pair<ll, ll> llP;
typedef pair<int, int> intP;
typedef std::priority_queue<int> IntPrioQueue; //Z->A
typedef std::priority_queue<int, std::vector<int>, std::greater<int> > IntReversePrioQueue; //A->Z

const int MAX = 64;
const double PI = 3.14159265358979323846;
const double EPS = 1e-12;
const int INF = 1<<29;
const int MOD = 1000000007;

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

int maze[MAX][MAX];

int H, W, ans;

bool range(int y, int x) {
    return (0 <= x && x < W && 0 <= y && y < H);
}

void dfs(int y, int x){
    maze[y][x] = 0;
    rep(8, d) {
        if (range(y+dy[d], x+dx[d]) && maze[y+dy[d]][x+dx[d]]) {
            dfs(y+dy[d], x+dx[d]);
        }
    }
    return;
}

void solve(void){
    while (1) {
        //input & init
        scanf("%d %d\n", &W, &H);
        if (W == 0 && H == 0) break;
        rep(H, y) rep(W, x) scanf("%d", &maze[y][x]);
        ans = 0;

        rep(H, y) rep(W, x) {
            if (maze[y][x]) {
                dfs(y, x);
                ans++;
            }
        }
        printf("%d\n", ans);
    }
}

int main(void){
  solve();
  return 0;
}

C++: #include <iostream>

using namespace std;

int w, h, cnt;
int island[50][50];
int dx[] = {1, 1, 0, -1, -1, -1, 0, 1};
int dy[] = {0, 1, 1, 1, 0, -1, -1, -1};

bool check(int nx, int ny){

  if(nx < 0 || w <= ny || ny < 0 || h < ny)return false;
  else return true;

}

void dfs(int sy, int sx){

  island[sy][sx] = 0;

  for(int i = 0 ; i < 8 ; i++){
    int nx = sx + dx[i];
    int ny = sy + dy[i];
    if(!check(nx, ny)) continue;
    if(island[ny][nx]) dfs(ny, nx);
  }
}

int main(void){

  while(cin >> w >> h, w + h){

    for(int i = 0 ; i < h ; i++)
      for(int j = 0 ; j < w ; j++)
	cin >> island[i][j];

    int cnt = 0;
    for(int i = 0 ; i < h ; i++){
      for(int j = 0 ; j < w ; j++){
	if(island[i][j] == 1){
	  dfs(i, j);
	  cnt++;
	}
      }
    }
    cout << cnt << endl;
  }
  return 0;
}