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>
#include <cctype>
#include <cstdio>
#include <math.h>
using namespace std;

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

int w,h,cnt,l[50][50];

void f(int x,int y){
	l[y][x]=0;
	for(int i=0;i<8;i++){
		int nx=x+dx[i];
		int ny=y+dy[i];
		if(nx>=0&&nx<w&&ny>=0&&ny<h&&l[ny][nx]==1)f(nx,ny);
	}
}

int main(){
	while(cin>>w>>h,w||h){
		cnt=0;
		for(int i=0;i<w*h;i++)cin>>l[i/w][i%w];
		for(int i=0;i<w*h;i++)if(l[i/w][i%w]==1){cnt++;f(i%w,i/w);}
		cout<<cnt<<endl;
	}
}

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

using namespace std;

int d[8][2] = {
	{-1, -1},
	{0, -1},
	{1, -1},
	{-1, 0},
	{1, 0},
	{-1, 1},
	{0, 1},
	{1, 1}
};

void func(int **a, int s, int t, int i, int j)
{
	if(a[i][j] == 0){
		return ;
	}
	a[i][j] = 0;
	
	for(int k = 0; k < 8; k++){
		if((i+d[k][0] >= 0 && i+d[k][0] < t) && (j+d[k][1] >= 0 && j+d[k][1] < s)){
			func(a, s, t, i+d[k][0], j+d[k][1]);
		}
	}
	
	return ;
}

int main(int argc, char **argv)
{
	int s, t, **a, c, t2, s2;
	
	while(1){
		cin >> s >> t;
		if(s == 0 && t == 0){
			break;
		} else if(s == 1 || t == 1){
			t2 = t+1;
			s2 = s+1;
		} else {
			t2 = t;
			s2 = s;
		}
		a = (int **)calloc(t2, sizeof(int));
		for(int i = 0; i < t; i++){
			a[i] = (int *)calloc(s2, sizeof(int));
			for(int j = 0; j < s; j++){
				cin >> c;
				a[i][j] = c;
			}
		}
		c = 0;
		
		for(int i = 0; i < t; i++){
			for(int j = 0; j < s; j++){
				if(a[i][j] == 1){
					c++;
					func(a, s, t, i, j);
				}
			}
		}
		cout << c << endl;
		
		for(int i = 0; i < s2; i++){
			free(a[i]);
		}
		free(a);
	}
	
	return 0;
}

C++: #include<iostream>
#include<vector>
#include<algorithm>
#include<cctype>
#include<utility>
#include<string>
#include<cmath>

#define REP(i, n) for(int i = 0;i < n;i++)
#define REPR(i, n) for(int i = n;i >= 0;i--)
#define FOR(i, m, n) for(int i = m;i < n;i++)
#define FORR(i, m, n) for(int i = m;i >= n;i--)
#define SORT(v, n) sort(v, v+n);
#define VSORT(v) sort(v.begin(), v.end());
#define llong long long
#define pb(a) push_back(a)
#define INF 999999999
using namespace std;
typedef pair<int, int> P;
typedef pair<llong, llong> LP;
typedef pair<int, P> PP;
typedef pair<llong, LP> LPP;


int w,h;
int dx[4] = {0, 1, 0, -1}, dy[4] = {-1, 0, 1, 0};

void dfs(vector<vector<int> > &map,int x,int y){
    /*for(int i = 0;i < h; i++){
        for(int j = 0; j < w; j++){
            cout << map[i][j] << " " ;
        }
        cout << endl;
    }*/
    //今いるところを-100に置き換える
    map[x][y] = -100;
    //移動方向をループ
    for(int dx = -1;dx <= 1;dx++){
        for(int dy = -1;dy <= 1;dy++){
            //x方向にdx,ｙ方向にdy移動した場所を(nx,ny)とする
            int nx = x + dx, ny = y + dy;
            if(0 <= nx && nx < h && 0 <= ny && ny < w && map[nx][ny] == 1){
                dfs(map,nx,ny);
            }
        }
    }
    return;
}

int solve(vector<vector<int> > &map,int h,int w){

    /*for(int i = 0;i < h; i++){
        for(int j = 0; j < w; j++){
            cout << map[i][j] << " " ;
        }
        cout << endl;
    }*/

    int ans = 0;
    for(int i = 0;i < h;i++){
        for(int j = 0;j < w;j++){
            if(map[i][j] == 1){
                //Wが残っているならばその場所からdfsを始める
                dfs(map,i,j);
                //ここで1つの水たまりが見つかったことになるので水たまりの個数を１つ足す
                ans++;
            }
        }
    }
    return ans;
}

int main(){

    
    

    while(cin >> w >> h){

        if(w == 0 && h == 0){
            break;
        }
        int ans = 0;
        vector<vector<int> > map(h,vector<int>(w));//周波数ベクトル列データ用の2次元配列

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

        ans = solve(map,h,w);

        cout << ans << endl;
    }

   


    

    return 0;
}

C++: #include<iostream>
#include<cstring>
using namespace std;
bool used[55][55];
int n,m;

void check(int x,int y){
	if(x<0 || n<=x || y<0 || m<=y)return;
	if(used[x][y])return;
	used[x][y]=true;
	for(int i=-1;i<=1;i++){
		for(int j=-1;j<=1;j++){
			check(x+i,y+j);
		}
	}
}

int main(){
	int i,j,k;
	int a,b,c;
	while(cin>>m>>n){
		if(!n)break;
		memset(used,false,sizeof(used));
		for(i=0;i<n;i++){
			for(j=0;j<m;j++){
				cin>>a;
				if(a==0)used[i][j]=true;
			}
		}
		a=0;
		for(i=0;i<n;i++){
			for(j=0;j<m;j++){
				if(!used[i][j])check(i,j),a++;
			}
		}
		cout<<a<<endl;
	}
}