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 <vector>
#include <string>
#include <algorithm>
#include <functional>
#include <tuple>
#include <sstream>
#include <set>

struct Node
{
  int data;
  Node* parent;
  int rank;
  Node() : data(-1), parent(this), rank(0){}
  Node& operator=(int data){ this->data = data; return *this; }
  Node* Find(){
    if (this == this->parent){
      return this;
    } else {
      auto root = this->parent->Find();
      this->parent = root;
      return root;
    }
  }
  static void Union(Node& lhs, Node& rhs){
    Node* lhs_root = lhs.Find();
    Node* rhs_root = rhs.Find();
    if (lhs_root->rank > rhs_root->rank){
      rhs_root->parent = lhs_root;
    } else if (rhs_root->rank > lhs_root->rank){
      lhs_root->parent = rhs_root;
    } else if (rhs_root != lhs_root){
      lhs_root->parent = rhs_root;
      rhs_root->rank += 1;
    }
    return;
  }
};

bool is_not_space(int c){ return c != ' '; }
std::string& ltrim(std::string& str){
  str.erase(str.begin(), std::find_if(str.begin(), str.end(), is_not_space));
  return str;
}
std::string& rtrim(std::string& str){
  str.erase(std::find_if(str.rbegin(), str.rend(), is_not_space).base(), str.end());
  return str;
}
std::string trim(std::string& str){ return ltrim(rtrim(str)); }
std::vector<std::pair<int, int>> const delta = {{-1,1}, {0,1}, {1,1}, {1,0}};

int main(void)
{
  std::string buff;
  while(true){
    std::getline(std::cin, buff);
    int w, h;
    {
      std::stringstream ss(buff);
      ss >> w;
      ss >> h;
    }
    if(w == 0 && h == 0){ break; }
    std::vector<Node> V((w+2)*(h+2));
    auto to_index = [=](int i, int j) -> size_t { return i*(w+2) + j; };
    std::vector<std::vector<int>> C(h+2, std::vector<int>(w+2, 0));
    for(int i=1; i<=h; ++i){
      std::getline(std::cin, buff);
      std::stringstream ss(buff);
      for(int j=1; j<=w; ++j){
        ss >> C[i][j];
        if(C[i][j] == 1){ V[to_index(i,j)].data = to_index(i,j); }
      }
    }
    for(int i=1; i<=h; ++i){
      for(int j=1; j<=w; ++j){
        if(C[i][j] == 0){ continue; }
        for(auto& d: delta){
          int di = d.first, dj = d.second;
          if(C[i+di][j+dj] == 1){ Node::Union(V[to_index(i,j)], V[to_index(i+di, j+dj)]); }
        }
      }
    }
    std::set<int> cluster;
    for(int i=1; i<=h; ++i){
      for(int j=1; j<=w; ++j){
        cluster.insert(V[to_index(i,j)].Find()->data);
      }
    }
    cluster.erase(-1);
    std::cout << cluster.size() << std::endl;

  }

  return 0;
}

C++: #include<iostream>
using namespace std;
void dfs(int,int);
int box[50][50];
int main(){
  int w,h,i,I,a;
  while(1){
    a=0;
    cin>>w>>h;
    if(w==0&&h==0) break;
    for(i=0;i<=h+1;i++){
      for(I=0;I<=w+1;I++){
	box[i][I]==0;
      }
    }
    for(i=1;i<=h;i++){
      for(I=1;I<=w;I++){
	cin>>box[i][I];
      }
    }
    for(i=1;i<=h;i++){
      for(I=1;I<=w;I++){
	if(box[i][I]==1){
	  dfs(i,I);
	  a++;
	}
      }
    }
    cout<<a<<endl;
  }
  return 0;
}
  void dfs(int i,int I){
  if(box[i][I]==0) return;
  box[i][I]=0;
  dfs(i,I+1);
  dfs(i+1,I+1);
  dfs(i+1,I);
  dfs(i+1,I-1);
  dfs(i,I-1);
  dfs(i-1,I-1);
  dfs(i-1,I);
  dfs(i-1,I+1);
  }

C++: #include <bits/stdc++.h>
#define REP(i,n,N) for(int i=n;i<N;i++)
#define p(S) cout<<S<<endl
using namespace std;

int chizu[51][51];

void labeling(int y,int x,int w,int h){
	chizu[y][x]=0;
	REP(dy,-1,2){
		REP(dx,-1,2){
			if(0 <= y+dy && y+dy < h && 0 <= x+dx && x+dx < w){
				if(chizu[y+dy][x+dx]){
					labeling(y+dy,x+dx,w,h);
				}
			}
		}
	}
}

int main(){
	int w,h;
	while(cin>>w>>h&&w&&h){

		int count=0;
		REP(i,0,h){
			REP(j,0,w){
				cin>>chizu[i][j];
			}
		}
		REP(i,0,h){
			REP(j,0,w){
				if(chizu[i][j]){
					count++;
					labeling(i,j,w,h);
				}
			}
		}

		p(count);
	}
	return 0;
}

C++: # include <iostream>

const int MAX_W = 50;
const int MAX_H = 50;

int w, h;

int c[MAX_H][MAX_W];

int dx[8] = { 0,-1,-1,-1,0,1,1,1 }, dy[8] = { -1,-1,0,1,1,1,0,-1 };

void dfs(int x, int y) {
	c[y][x] = 0;
	for (int i = 0; i < 8; ++i) {
		int nx = x + dx[i];
		int ny = y + dy[i];
		if (nx<0 || ny<0 || nx>w || ny>h)
			continue;
		if (c[ny][nx])
			dfs(nx, ny);
	}
}

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

int main() {
	while (1) {
		std::cin >> w >> h;
		if ((w + h) == 0)
			break;
		for (int i = 0; i < h; ++i) {
			for (int j = 0; j < w; ++j)
				std::cin >> c[i][j];
		}
		std::cout << solve() << std::endl;
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
using namespace std;
int needx[]={-1,0,1,0,1,1,-1,-1};
int needy[]={0,1,0,-1,1,-1,1,-1};
//??¶?????¨???false????????????true???????????¢??°//
bool land(int x,int y,vector<vector<bool> >& cango){
    if(cango[x][y]){
        cango[x][y]=false;
        for(int i=0;i<8;i++){
            int nextx=x+needx[i];
            int nexty=y+needy[i];
            if(cango[nextx][nexty])
                bool flag=land(nextx,nexty,cango);
            }
    return true;
     }else{
return false;
    }
}
int main(void){
    int input;
	int w,h;
	while(1){
cin>>w>>h;
if(h==0)break;
    vector<vector<bool> > cango(h+2,vector<bool>(w+2,false));
    for(int i=1;i<=h;i++){
        for(int j=1;j<=w;j++){
            cin >>input;
            if(input==1){
cango[i][j]=true;
            }
        }
    }
  
    int t=0;
for(int i=1;i<=h;i++){
    for(int j=1;j<=w;j++){
        if(land(i,j,cango)){
            t++;
        }
    }
}
cout <<t<<endl;
	}
return 0;
}