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 < H && 0 <= ny && ny < W && 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);
	  res++;
	  /*cout << endl;
	  for(int b = 0 ; b < H ; b++) {
	    for(int a = 0 ; a < W ; a++) {
	      cout << field[b][a] << ' ';
	    }
	    cout << endl;
	  }
	  cout << endl;*/
	}
      }
    }
    cout << res << endl;
  }
  return 0;
}

C++: #include "bits/stdc++.h"

using namespace std;

typedef pair<int, int> P;

int main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

    int w,h;
    int dx[8]={1,1,1,0,-1,-1,-1,0},dy[8]={-1,0,1,1,1,0,-1,-1};
    while(cin>>w>>h,w||h){
        vector< vector<int> > field(h,vector<int>(w));
        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                cin>>field[i][j];
            }
        }
        int res=0;
        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                if(field[i][j]){
                    //cout<<i<<" "<<j<<endl;
                    queue<P> q;
                    field[i][j]=0;
                    q.push(P(i,j));
                    while(!q.empty()){
                        P p=q.front();q.pop();
                        for(int k=0;k<8;k++){
                            int nx=p.first+dx[k],ny=p.second+dy[k];
                            if(nx<0||h<=nx||ny<0||w<=ny) continue;
                            if(field[nx][ny]==0) continue;
                            field[nx][ny]=0;
                            q.push(P(nx,ny));
                        }
                    }
                    res++;
                }
            }
        }
        cout<<res<<endl;
    }
}

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

vector<vector<int>>tisei;
int tate, yoko;
void shima(int a, int b) {
	tisei[a][b] = 0;
	for (int c = a-1; c < a+2; c++) {
		for (int d = b - 1; d < b + 2; d++) {
			if (c > -1 && d > -1 && c< tate&d < yoko&&tisei[c][d])shima(c, d);
		}
	}
}
int main() {
	int a, b;
	while (cin >> a >> b, a | b) {
		tate = b;
		yoko = a;
		tisei.clear();
		for (int c = 0; c < b; c++) {
			vector<int>o(a);
			for (int e = 0; e < a; e++) {
				cin >> o[e];
			}
			tisei.push_back(o);
		}
		int s = 0;
		for (int g = 0; g < b; g++) {
			for (int h = 0; h < a; h++) {
				if (tisei[g][h]) { s++;  shima(g, h); }
			}
		}
		cout << s << endl;
	}
}

C++: #include<iostream>
#include<fstream>

using namespace std;

	ifstream fin;
	ofstream fout;

	//http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=1160&lang=jp

	int gomi = 0;

	int a[52][52] = {};
	int check(int, int);

	int main(){

		fin.open("input.txt");
		fout.open("output.txt");

		//		int w = 0, h = 0;
		int width = 0, height = 0;
		int count = 0;


		while (1){
			for (int i = 0; i < 50; i++)
				for (int j = 0; j < 50; j++)
					a[i + 1][j + 1] = 0;

			fin >> width >> height;
			if (width == 0 && height == 0)break;

			for (int i = 0; i < height; i++){
				for (int j = 0; j < width; j++){
					//初期化
					gomi = a[i + 1][j + 1] = 0;

					fin >> a[i + 1][j + 1];
				}
			}

			for (int i = 0; i < height; i++){
				for (int j = 0; j < width; j++){
					if (a[i + 1][j + 1] == 1){
						check(i + 1, j + 1);
//						a[i + 1][j + 1] = 1;
						count++;
//						cout << i + 1 << "  " << j + 1 << endl;
					}
				}
			}
			cout << count << endl;
			fout << count << endl;

			//初期化
			count = 0;
			for (int i = 0; i < height; i++){
				for (int j = 0; j < width; j++){
					a[i + 1][j + 1] = 0;
				}
			}
		}
	}

	int check(int y, int x){
		for (int i = -1; i <= 1; i++){
			for (int j = -1; j <= 1; j++){
				if (i + j != 0 || i - j != 0){
					if (a[y + i][x + j] == 1){
						a[y + i][x + j] = 0;
						check(y + i, x + j);
					}
				}
			}
		}
		return 0;
	}

/*	int check(int y, int x){
		if (a[y + 1][x] == 1){
			a[y + 1][x] = 0;
			check(y + 1, x);
		}
		//-----------------------------
		if (a[y][x + 1] == 1){
			a[y][x + 1] = 0;
			check(y, x + 1);
		}
		//-----------------------------
		if (a[y - 1][x] == 1){
			a[y - 1][x] = 0;
			check(y - 1, x);
		}
		//-----------------------------
		if (a[y][x - 1] == 1){
			a[y][x - 1] = 0;
			check(y, x - 1);
		}
		//-----------------------------
		if (a[y + 1][x + 1] == 1){
			a[y + 1][x + 1] = 0;
			check(y + 1, x + 1);
		}
		//-----------------------------
		if (a[y + 1][x - 1] == 1){
			a[y + 1][x - 1] = 0;
			check(y + 1, x - 1);
		}
		//-----------------------------
		if (a[y - 1][x + 1] == 1){
			a[y - 1][x + 1] = 0;
			check(y - 1, x + 1);
		}
		//-----------------------------
		if (a[y - 1][x - 1] == 1){
			a[y - 1][x - 1] = 0;
			check(y - 1, x - 1);
		}
		//-----------------------------
		return 0;
	}*/