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 <algorithm>

using namespace std;

int tizu[52][52];

void check(int i, int j) {
	tizu[i][j] = 0;
	for (int k = -1; k <= 1; k++) {
		for (int l = -1; l <= 1; l++) {
			if (tizu[i+k][j+l] == 1) {
				check(i+k,j+l);
			}
		}
	}
	return;
}

int main() {
	int w, h;
	while (cin >> w >> h) {
		if (w == 0 && h == 0) {
			break;
		}
		for (int i = 0; i < 52; i++) {
			for (int j = 0; j < 52; j++) {
				tizu[i][j] = 0;
			}
		}
		int counter = 0;
		for (int i = 1; i <= h; i++) {
			for (int j = 1; j <= w; j++) {
				cin >> tizu[i][j];
			}
		}
		for (int i = 1; i <= h; i++) {
			for (int j = 1; j <= w; j++) {
				if (tizu[i][j] == 1) {
					counter++;
					check(i,j);
				}
			}
		}
		cout << counter << endl;
	}
	return 0;
}

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

// 入力
int H, W;
vector<vector<int> > field;

// 探索
void dfs(int h, int w) {
    field[h][w] = 0;

    // 八方向を探索
    for (int dh = -1; dh <= 1; ++dh) {
        for (int dw = -1; dw <= 1; ++dw) {
            int nh = h + dh, nw = w + dw;
            
            // 場外アウトしたり、0 だったりはスルー
            if (nh < 0 || nh >= H || nw < 0 || nw >= W) continue;
            if (field[nh][nw] == 0) continue;

            // 再帰的に探索
            dfs(nh, nw);
        }
    }
}

int main() {
    // 入力受け取り
    while (cin >> W >> H) {
        if (H == 0 || W == 0) break;
        field.assign(H, vector<int>(W, 0));
        for (int h = 0; h < H; ++h) for (int w = 0; w < W; ++w) cin >> field[h][w];

        // 探索開始
        int count = 0;
        for (int h = 0; h < H; ++h) {
            for (int w = 0; w < W; ++w) {
                if (field[h][w] == 0) continue; // 残島じゃなかったらスルー
                dfs(h, w);
                ++count;
            }
        }
        cout << count << endl;
    }
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll = long long;
constexpr ll MOD = 1000000007;
constexpr ll INF = 1ll<<60;

ll field[60][60];
bool f[60][60];
ll W, H;

void dfs(ll h, ll w)
{
	if (f[h][w]) return;
	f[h][w] = true;
	for (ll i = -1; i <= 1; ++i)
		for (ll j = -1; j <= 1; ++j)
		{
			ll nw = w + i;
			ll nh = h + j;
			if (nw < 0 || nw > W || nh < 0 || nh > H) continue;
			if (field[nh][nw])
				dfs(nh, nw);
		}
}

int main(int argc, char **argv)
{
	while (cin >> W >> H, true)
	{
		if (W == 0 && H == 0) break;
		memset(f, 0, sizeof f);
		memset(field, 0, sizeof field);

		vector<pair<ll, ll>> search;
		search.reserve(50*50);
		for (ll h = 0; h < H; ++h)
			for (ll w = 0; w < W; ++w)
			{
				cin >> field[h][w];
				if (field[h][w] == 1)
				{
					search.push_back(pair<ll, ll>(h, w));
					// std::cout << "(h, w) : " << h << ", " << w << std::endl;
				}
			}
		
		ll res{0};
		for (ll i = 0; i < (ll)search.size(); ++i)
		{
			if (!f[search[i].first][search[i].second])
			{
				// std::cout << "(h, w) : " << search[i].first << ", " << search[i].second << std::endl;
				dfs(search[i].first, search[i].second);
				++res;
			}
		}
		std::cout << res << std::endl;

	}
}

C++: #include<bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int dx[8]={1,0,-1,0,1,1,-1,-1};
int dy[8]={0,1,0,-1,1,-1,1,-1};
bool seen[50][50];
int G[50][50];

void dfs(int x,int y,int h,int w){
    seen[x][y]=true;

    rep(i,8){
        int nx=x+dx[i];
        int ny=y+dy[i];
        if(nx<0||nx>h-1||ny<0||ny>w-1)continue;
        if(seen[nx][ny])continue;
        if(G[nx][ny]==0)continue;
        dfs(nx,ny,h,w);
    }
}

int main(){
    while(1){
        int h,w;
        int ans=0;
        cin>>w>>h;
        if(w==0&&h==0)break;
        rep(i,h)rep(j,w)cin>>G[i][j];
        rep(i,50)rep(j,50)seen[i][j]=false;
        rep(i,h)rep(j,w){
            if(seen[i][j]==false&&G[i][j]==1){
                ans++;
                dfs(i,j,h,w);
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}

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

int islands=0;
int w,h;
int field[49][49];
void bfs(int, int);

int main(){

  while(cin>>w>>h&&w!=0&&h!=0){

    for(int i=0;i<50;i++){
      for(int j=0;j<50;j++){
        field[i][j] = 0;
      }
    }

    for(int j=0;j<h;j++){
      for(int i=0;i<w;i++){
        cin >> field[i][j];
//        cout << field[i][j] << " ";
      }
  //    cout << endl;
    }
   // cout << endl;
    int ans=0; 

    for(int i=0;i<w;i++){
      for(int j=0;j<h;j++){
        if(field[i][j]==1){
          field[i][j]=0;
          bfs(i,j);
          ans++;
        }
      }
    }
    /*   if(w==5&&h==4){
         for(int i=0;i<w;i++){
         for(int j=0;j<h;j++){
         cout << field[i][j] << " ";
         }
         cout << endl;
         }
         }*/
    cout << ans << endl;
  }

  return 0;
}

void bfs(int x, int y){
  if(x-1>=0&&field[x-1][y]==1){
    field[x-1][y]=0;
    bfs(x-1,y);
  }
  if(x+1<w&&field[x+1][y]==1){
    field[x+1][y]=0;
    bfs(x+1,y);
  }
  if(y-1>=0&&field[x][y-1]==1){
    field[x][y-1]=0;
    bfs(x,y-1);
  }
  if(y+1<h&&field[x][y+1]==1){
    field[x][y+1]=0;
    bfs(x, y+1);
  }
  if(x-1>=0&&y-1>=0&&field[x-1][y-1]==1){
    field[x-1][y-1]=0;
    bfs(x-1,y-1);
  }
  if(x+1<w&&y-1>=0&&field[x+1][y-1]==1){
    field[x+1][y-1]=0;
    bfs(x+1,y-1);
  }
  if(x-1>=0&&y+1<h&&field[x-1][y+1]==1){
    field[x-1][y+1]=0;
    bfs(x-1,y+1);
  }
  if(x+1<w&&y+1<h&&field[x+1][y+1]==1){
    field[x+1][y+1]=0;
    bfs(x+1,y+1);
  }
  return;
}