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>
using namespace std;

int w, h;
int field[60][60];

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

    for (int i = -1; i <= 1; i++) {
        for (int j = -1; j <= 1; j++) {
            int dx = x + i, dy = y + j;
            if (dx < 0 || dx >= h || dy < 0 || dy >= w) continue;
            if (field[dx][dy] == 0) continue;
            dfs(dx, dy);
        }
    }
}

int main() {
    while (1) {
        cin >> w >> h;
        if (w == 0 && h == 0) break;

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

        int cnt = 0;
        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {
                if (field[i][j] == 0) continue;
                dfs(i, j);
                cnt++;
            }
        }

        cout << cnt << endl;
    }

    return 0;
}

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

int main(){
    int w, h, t0, t1, result, temp;
    pair<int, int> cur;
    vector<int> dx = {1, 1, 1, 0, 0, -1, -1, -1};
    vector<int> dy = {1, 0, -1, 1, -1, 1, 0, -1};
    while(true){
        cin >> w >> h;
        if(w == 0 && h == 0) break;
        vector<LL> c(h);
        vector<LL> seen(h);
        vector<pair<int, int>> f;
        rep(i, h) rep(j, w){
            cin >> temp;
            c[i] |= (LL)temp<<j;
            if(temp) f.push_back(make_pair(i, j));
        }
        result = 0;
        stack<pair<int, int>> stk;
        for(auto &&pos : f){
            if(!(seen[pos.first]&1LL<<pos.second)) ++result;
            stk.push(make_pair(pos.first, pos.second));
            while(!stk.empty()){
                cur = stk.top();
                stk.pop();
                rep(i, 8){
                    t0 = cur.first + dy[i];
                    t1 = cur.second + dx[i];
                    if(t0==-1 || t0==h || t1==-1 || t1==w || seen[t0]&1LL<<t1 || !(c[t0]&1LL<<t1)) continue;
                    stk.push(make_pair(t0, t1));
                    seen[t0] |= 1LL<<t1;
                }
            }
        }
        cout(result);
    }
}

C++: #include <iostream>
using namespace std;
void dfs(int,int);
int data[52][52];
int main(){
  int w,h,i,j,cnt;
  while(1){
    cnt=0;
    cin >> w >> h;
    if(w==0&&h==0) break;
    for(i=0;i<=h+1;i++){
      for(j=0;j<=w+1;j++){
	data[i][j]=0;
      }
    }
    for(i=1;i<=h;i++){
      for(j=1;j<=w;j++){
	cin >> data[i][j];
      }
    }
    for(i=1;i<=h;i++){
      for(j=1;j<=w;j++){
        if(data[i][j]==1){
	  dfs(i,j);
	  cnt++;
	}
      }
    }
    cout << cnt << endl;
  }
  return 0;
}
void dfs(int i,int j){
  if(data[i][j]==0) return ;
  data[i][j]=0;
  dfs(i-1,j);
  dfs(i+1,j);
  dfs(i,j-1);
  dfs(i,j+1);
  dfs(i-1,j-1);
  dfs(i-1,j+1);
  dfs(i+1,j-1);
  dfs(i+1,j+1);
}

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

int c[50][50];
int w, h;

void dfs(int x, int y) {
  c[y][x] = 0;
  for (int i = -1; i <= 1; i++) {
    for (int j = -1; j <= 1; j++) {
      int nx = x + i;
      int ny = y + j;
      if (c[ny][nx] == 1 && 0 <= nx && nx < w && 0 <= ny && ny < h)
	dfs(nx, ny);
    }
  }
}

int search() {
  int count = 0;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (c[i][j] == 1) {
	dfs(j, i);
	count++;
      }
    }
  }
  return count;
}

int main() {
  while (true) {
    cin >> w >> h;
    if (w == 0 && h == 0) return 0;

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

    int ans = search();
    cout << ans << endl;
  }
}

C++: 
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <string>
#include <queue>
#include <algorithm>
#include <math.h>
#include <utility>
#include <set>
#include <map>
#define INF 100000
#define rep(i,n) for(int i =0;i<n;i++)
using namespace std;
typedef long long int ll;

#define MAX 5000

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


void dfs(int x, int y){
    if(x<0||x>w||y<0||y>h) return;
    for (int i=-1; i<=1 and x+i<=h; i++) {
        for (int j=-1; j<=1 and y+j<=w; j++) {
            if (G[x+i][y+j]==1) {
                G[x+i][y+j]=0;
                dfs(x+i,y+j);
            }
        }
    }
}


int main(){
    for(;;){
        cin >> w >> h;
        if(w==0 and h == 0) break;
        int ans=0;
        for (int i=0; i<=h; i++) {
            for (int j=0; j<=w; j++) {
                G[i][j]=0;
            }
        }
        for (int i = 0; i<h;i++) {
            for (int j=0; j < w; j++) {
                cin >> G[i][j];
            }
        }
        for (int i=0; i<h; i++) {
            for (int j=0; j<w; j++) {
                if (G[i][j]==1) {
                    G[i][j]=0;
                    ans++;
                    dfs(i,j);
                }
            }
        }
        cout << ans <<endl;
    }
    return 0;
}