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;

// 入力
int H, W;
vector<vector<int>> field(H, vector<int>(W, 0));

// 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 <iostream>
#include <vector>

int flag[52][52];
int c[52][52];
std::vector<std::vector<int> > land;
std::vector<int> v(2);
int island;
int w, h;

bool search(int x, int y){
  flag[x][y] = 1;
  for(int dx = -1; dx < 2; dx++){
    for(int dy = -1; dy < 2; dy++){
      if(c[x + dx][y + dy] == 1 && flag[x + dx][y + dy] == 0){
        v[0] = x + dx;
        v[1] = y + dy;
        land.push_back(v);
        flag[x + dx][y + dy] = 1;
      }
    }
  }
  land.erase(land.begin());
  return land.empty();
}

int main(){
  while(true){
    std::cin >> w >> h;
    if(w == 0 && h == 0){
      break;
    }
    else{
      island = 0;
      for(int i = 1; i <= h; i++){
        for(int j = 1; j <= w; j++){
          std::cin >> c[j][i];
          flag[j][i] = 0;
        }
      }

      for(int i = 1; i <= w; i++){
        for(int j = 1; j <= h; j++){
          if(c[i][j] == 1 && flag[i][j] == 0){
            v[0] = i;
            v[1] = j;
            land.push_back(v);
            while(true){
              if(search(land[0][0], land[0][1])) break;
            }
            island++;
          }
        }
      }
      std::cout << island << std::endl;
    }
  }
  return 0;
}

C++: #include <iostream>
#include <vector>
using namespace std;
#define MAX 50

int c[MAX][MAX];

void dfs(int w, int h, int x, int y);
int main(int argc, char const *argv[]){
    int w, h, ans;

    while (cin>>w>>h, w || h){
        ans = 0;
        for (int i = 0; i < h; i++){
            for (int j = 0; j < w; j++){
                cin>>c[i][j];
            }
        }
        for (int i = 0; i < w; i++){
            for (int j = 0; j < h; j++){
                if (c[i][j] == 1){
                    dfs(w, h, i, j);
                    ans++;

                    for (int i = 0; i < w; i++){
                        for (int j = 0; j < h; j++){
                            cout<<c[i][j]<<" ";
                        }
                        cout<<'\n';
                    }
                    cout<<'\n';
                }
            }
        }
        cout<<ans<<endl;
    }

    return 0;
}

void dfs(int w, int h, int x, int y){
    int dx[8] = {1, 1, 0, -1, -1, -1, 0, 1};
    int dy[8] = {0, 1, 1, 1, 0, -1, -1, -1};
    c[x][y] = 0;

    for (int i = 0; i < 8; i++){
        int nx = x + dx[i];
        int ny = y + dy[i];

        if (0 <= nx && nx < w && 0 <= ny && ny < h && c[nx][ny] == 1){
            dfs(w, h, nx, ny);
        }
    }
    return;
}

C++: //#include <bits/stdc++.h>
#include <iostream>
#include <cstring>
using namespace std;

int mp[50][50]={0};
int dx[8]={-1,-1,-1,0,0,1,1,1};
int dy[8]={-1,0,1,-1,1,-1,0,1};
 int W,H;
 void dfs(int w,int h);
int main(){
 
    while(true){
        
    int cnt=0;

    cin >>W >>H;
    if(W==0 && H==0) break;
    for (int i=0;i<H;i++){
        for(int j=0;j<W;j++){
            cin >> mp[i][j];
        }
    }
    
//    memcpy(mp1,mp,sizeof(mp));
    
    for (int i=0;i<H;i++){
        for(int j=0;j<W;j++){
            if (mp[i][j]==1){
                cnt++;
                dfs(j,i);
            }
        }
    }
   cout <<cnt<<endl;
    } 

}

void dfs(int w,int h){
    mp[h][w]=0;
    int nx,ny;
    for (int i=0;i<8;i++){
        nx=w+dx[i];ny=h+dy[i];
        if(0<=nx && nx<W && 0<=ny && ny<H && mp[ny][nx]==1){
            dfs(nx,ny);
        }

    }

}

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

int w,h;
int c[50][50];
vector<vector<int> > visited;
int dx[]={1,1,0,-1,-1,-1,0,1};
int dy[]={0,-1,-1,-1,0,1,1,1};

bool dfs(int x,int y){
    if(visited[x][y]) return false;
    visited[x][y]=1;

    for(int d=0;d<8;d++){
        int i=x+dx[d];
        int j=y+dy[d];
        if(0<=i&&i<h&&0<=j&&j<w){
            if(c[i][j]){
                dfs(i,j);
            }  
        }
    }
    return true;
}

int main(){
    visited.assign(50,vector<int>(50,0));
    cin>>w>>h;
    for(int i=0;i<h;i++){
        for(int j=0;j<w;j++){
            cin>>c[i][j];
        }
    }
    int cnt=0;
    for(int i=0;i<h;i++){
        for(int j=0;j<w;j++){
            if(c[i][j]){
                cnt+=dfs(i,j);
            }
        }
    }

    cout<<cnt<<endl;
    return 0;
}