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 <cstdio>
using namespace std;
char field[51][51];
int W, H;

void dfs(int x, int y) {
  //cout << "field[x][y] = " << field[x][y] << endl;
  field[x][y] = '0';
  
  for(int dx = -1 ; dx <= 1 ; dx++) {
    for(int dy = -1 ; dy <= 1 ; dy++) {
      int nx = x + dx, ny = y + dy;
      if(0 <= nx && nx < W && 0 <= ny && ny < H && field[nx][ny] == '1') dfs(nx, ny);
    }
  }
}

int main(void) {
  while(cin >> W >> H, W != 0 && H != 0) {
    int res = 0;
    for(int i = 0 ; i < H ; i++)
      for(int j = 0 ; j < W ; j++) cin >> field[i][j];
    
    for(int i = 0 ; i < W ; i++) {
      for(int j = 0 ; j < H ; j++) {
	if(field[i][j] == '1') {
	  dfs(i, j);
	  
	  /*cout << endl;
	  for(int b = 0 ; b < H ; b++) {
	    for(int a = 0 ; a < W ; a++) {
	      cout << field[b][a] << ' ';
	    }
	    cout << endl;
	  }
	  cout << endl;*/
	  res++;
	}
      }
    }
    cout << res << endl;
  }
  return 0;
}

C++: #include<stdio.h>
#include<iostream>

int field[51][51];
int w,h;

void land(int x,int y){
	field[x][y]=0;

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

int main(void){

	int kazu=0;

	while(1){

	scanf("%d %d",&w,&h);

	if(w==0&&h==0) break;

	kazu=0;

	for(int i=0;i<h;i++){
		for(int j=0;j<w;j++){
			scanf("%d",&field[j][i]);
		}
	}

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

			if(field[j][i]==1){
				land(j,i);
				kazu++;
			}

		}
	}

	printf("%d\n",kazu);
	}

	return 0;
}

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

int H, W;
vector<vector<int>> field(H, vector<int>(W));
vector<vector<bool>> seen(H, vector<bool>(W));

const int dh[8] = {1, 0, -1, 0, 1, 1, -1, -1};
const int dw[8] = {0, 1, 0, -1, 1, -1, 1, -1};

void dfs(int h, int w)
{
    seen[h][w] = true;
    int nh, nw;
    for (int i=0; i<8; i++)
    {
        nh = h + dh[i];
        nw = w + dw[i];
        if (nh<0 || nh>=H || nw<0 || nw>=W) continue;
        if (seen[nh][nw]) continue;
        if (field[nh][nw]==0) continue;
        dfs(nh, nw);
    }
}

int main()
{
    while (cin >> W >> H)
    {
        if (W==0 || H==0) break;
        field.resize(H);
        seen.resize(H);
        for (int h=0; h<H; h++)
        {
            field[h].resize(W);
            seen[h].resize(W);
        }
        for (int h=0; h<H; h++)
        {
            for (int w=0; w<W; w++) 
            {
                cin >> field[h][w];
                seen[h][w]=false;
            }
        }
        int answer=0;
        for (int h=0; h<H; h++)
        {
            for (int w=0; w<W; w++)
            {
                if (seen[h][w]==false && field[h][w]==1) dfs(h, w), answer++;
            }
        }
        cout << answer << endl;
    }
}

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

int MAP(vector<vector<int>> &m, int i, int j){
	int w = m[0].size();
	int h = m.size();

	if(!(0 <= i && i < h && 0 <= j && j < w)){
		return 0;
	}

	if(m[i][j] == 0){
		return 0;
	}
	else if(m[i][j] = 1){
		m[i][j] = 0;
		MAP(m, i - 1, j - 1);
		MAP(m, i, j - 1);
		MAP(m, i + 1, j - 1);
		MAP(m, i - 1, j);
		MAP(m, i + 1, j);
		MAP(m, i - 1, j + 1);
		MAP(m, i, j + 1);
		MAP(m, i + 1, j + 1);
	}
	return 1;
}

int main(){
	int w, h;

	while(true){
		int count = 0;
		cin >> w >> h;

		if(w == 0 && h == 0){
			break;
		}

		vector<vector<int>> map(h, vector<int>(w, 0));

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

		for(int i = 0; i < h; i++){
			for(int j = 0; j < w; j++){
				count += MAP(map, i , j);
			}
		}

		cout << count << endl;
	}
}

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

#define rep(i, n) for (int i = 0; i < (n); i++)

template <class T>
T next()
{
    T x;
    cin >> x;
    return (x);
}

int w, h;
vector<vector<int>> islands;

void dfs(int ii, int jj)
{
    islands[jj][ii] = 0;
    for (int i = ii - 1; i <= ii + 1; i++)
    {
        for (int j = jj - 1; j <= jj + 1; j++)
        {
            if (i < 0 || i == w || j < 0 || j == h)
            {
            }
            else if (islands[j][i] > 0)
            {
                dfs(i, j);
            }
        }
    }
}

int main()
{
    vector<int> ans;
    while (true)
    {
        int cnt = 0;
        w = next<int>();
        h = next<int>();
        if (w + h == 0)
        {
            break;
        }
        islands.resize(h);
        rep(j, h)
        {
            islands[j].resize(w);
            rep(i, w)
            {
                cin >> islands[j][i];
            }
        }
        rep(j, h)
        {
            rep(i, w)
            {
                if (islands[j][i] > 0)
                {
                    cnt++;
                    dfs(i, j);
                }
            }
        }
        ans.push_back(cnt);
    }
    for (int i : ans)
    {
        cout << i << endl;
    }
}