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 <algorithm>
#include <bitset>
#include <cmath>
#include <ctime>
#include <iostream>
#include <list>
#include <map>
#include <math.h>
#include <numeric>
#include <queue>
#include <set>
#include <stack>
#include <stdio.h>
#include <string>
#include <tuple>
#include <vector>
 
using namespace std;
using Graph = vector<vector<int>>;

#define rep(i,n) for(int i = 0; i < (n); i++)
#define all(a) begin(a),end(a)
 
typedef long long ll;
typedef pair<int,int> P;
const int inf=1000000007;
const ll mod=1000000007;
const double PI=3.14159265358979323846;
 
int dx[] = {1,-1,0,0};
int dy[] = {0,0,1,-1};
 
ll gcd(ll a, ll b){
  if (b==0) return a;
  else return gcd(b,a%b);
}
 
int cans(bool f){
  if(f) cout << "Yes" << endl;
  else cout << "No" << endl;
  return 0;
}





int W,H;
vector<vector<int>> field;



void dfs(int y,int x){
  field[y][x] = 0;
  for(int i = -1; i <= 1; i++){
    for(int j = -1; j <= 1; j++){
      
      int nx,ny; 
      nx = x + i;
      ny = y + j;
      if (ny < 0 || ny >= H || nx < 0 || nx >= W || field[ny][nx] == 0) continue;
      dfs(ny,nx);
    }
  }
}

int main(){
  while(cin >> W >> H){
    if(W == 0 || H == 0) break;
    field.assign(H,vector<int>(W,0));
    rep(i,H){
      rep(j,W) cin >> field[i][j];
    }
    
    int ans = 0;
    rep(i,H){
      rep(j,W){
	if(field[i][j] == 0) continue;
	ans++;
	dfs(i,j);
      }
    }
    cout << ans << endl;
  }
}












// 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<bits/stdc++.h>
using namespace std;
int w,h,c[50][50],ans;
vector<int> out;
bool dfs(int x,int y);
int main(){
  while(1){
    ans = 0;
    for(int i=0;i<50;i++){
      for(int l=0;l<50;l++){
        c[i][l] = 0;
      }
    }
    cin >> w >> h;
    if(w == 0 && h == 0){
      break;
    }
    for(int i=0;i<h;i++){
      for(int l=0;l<w;l++){
         cin >> c[l][i];
      }
    }
    for(int i=0;i<h;i++){
      for(int l=0;l<w;l++){
        if(c[l][i] == 1){
          dfs(l,i);
          ans++;
        }
      }
    }
    out.push_back(ans);
  }
  for(int i=0;i<out.size();i++){
    cout << out[i] << endl;
  }
}
bool dfs(int x,int y){
  if(x<0 || x>=w || y<0 || y>=h || c[x][y] == 0) return false;
  c[x][y] = 0;
  for(int dx=-1;dx<=1;dx++){
    for(int dy=-1;dy<=1;dy++){
      if(dfs(x+dx,y+dy)){
        return true;
      }
    }
  }
  return false;
}

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

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

int f(int x, int y){
    if(x >= w || x < 0 || y >= h || y < 0) return 0;
    if(flag[x][y] == 1 || c[x][y] == 0) return 0;
    flag[x][y] = 1;
    f(x+1,y);
    f(x-1,y);
    f(x,y+1);
    f(x,y-1);
    f(x+1,y+1);
    f(x+1,y-1);
    f(x-1,y+1);
    f(x-1,y-1);
    return 1;
}

int main(){
    do{
        int sum = 0;
        cin >> w >> h;
        if(w == 0 && h == 0) return 0;
        for(int y = 0; y < h; y++){
            for(int x = 0; x < w; x++){
                cin >> c[x][y];
                flag[x][y] = 0;
            }
        }
        for(int y = 0; y < h; y++){
            for(int x = 0; x < w; x++){
                sum += f(x,y);
            }
        }
        cout << sum << endl;
    }while(true);

    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++;
                }
            }
        }
        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;
}