Go: ///
// File:  1160.go
// Author: ymiyamoto
//
// Created on Sun Mar  4 20:45:57 2018
//
package main

import (
	"fmt"
)

var w, h int
var graph [][]string

func dfs(visited [][]bool, x, y int) {
	visited[x][y] = true

	for i := -1; i <= 1; i++ {
		for j := -1; j <= 1; j++ {
			dx := x + i
			dy := y + j
			if 0 <= dx && dx < h && 0 <= dy && dy < w && graph[dx][dy] == "1" && !visited[dx][dy] {
				dfs(visited, dx, dy)
			}
		}
	}
}

func main() {
	for {
		fmt.Scan(&w, &h)
		if w == 0 && h == 0 {
			break
		}

		graph = make([][]string, h)
		for i := range graph {
			graph[i] = make([]string, w)
		}

		for i := 0; i < h; i++ {
			for j := 0; j < w; j++ {
				var s string
				fmt.Scan(&s)
				graph[i][j] = s
			}
		}

		visited := make([][]bool, h)
		for i := range visited {
			visited[i] = make([]bool, w)
		}

		count := 0
		for i := range graph {
			for j := range graph[i] {
				if graph[i][j] == "1" && !visited[i][j] {
					dfs(visited, i, j)
					count++
				}
			}
		}

		fmt.Println(count)
	}
}

C++: 
/*
Problem

Category
DFS

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

考察:


Date: 2020/04/14
*/

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define int long long

/* ==== declarations ====== */
// functions
void solve();
void getInput();

// global variables
int w, h;
vector<vector<bool>> C;
vector<vector<int>> color;
int currentColor = 1;


/* ======================== */

signed main(){
    while(true){
        getInput();
        solve();
    }
    return 0;
}

void getInput() {
    cin>>w>>h;
    if(!w and !h) {exit(0);}
    C = vector<vector<bool>>(h, vector<bool>(w, false));
    color = vector<vector<int>>(h, vector<int>(w, 0));
    for(int i=0; i<h; i++) {
        for(int j=0; j<w; ++j) {
            bool c;
            cin>>c;
            C[i][j] = c;
        }
    }
}

void dfs(int i, int j) {
    if (i < 0 or j < 0 or i >= h or j >= w) return;
    if (!C[i][j]) return;
    if (color[i][j]) return;
    color[i][j] = currentColor;
    
    for(int a: {i-1, i, i+1})
        for(int b: {j-1, j, j+1})
            dfs(a, b);
    
}


void solve() {
    for(int i=0; i<h; i++) {
        for(int j=0; j<w; ++j) {
            dfs(i, j);
            currentColor++;
        }
    }
    set<int> colorSet {0};
    for(int i=0; i<h; i++) {
        for(int j=0; j<w; ++j) {
            colorSet.insert(color[i][j]);
        }
    }
    cout<<colorSet.size()-1<<endl;
}

C++: #include <iostream>

using namespace std;

// 0: 海, 1: 陸
int board[50][50] = {{0}};

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

bool DFS(int i, int j, int w, int h) {
  if (i < 0 || i >= h || j < 0 || j >= w) return false;
  if (!board[i][j]) return false;

  board[i][j] = 0;
  for (int d = 0; d < 8; ++d)
    DFS(i + dy[d], j + dx[d], w, h);

  return true;
}

int main() {
  for (;;) {
    int w, h;
    cin >> w >> h;
    if (w == 0 && h == 0) break;

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

    int ans = 0;
    for (int i = 0; i < h; ++i) {
      for (int j = 0; j < w; ++j) {
        if (DFS(i, j, w, h)) ++ans;
      }
    }
    cout << ans << endl;
  }
  return 0;
}

C++: #define LOCAL
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstring>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;
using ll = long long;
using P = pair<int, int>;

#define REP(i, x) for (int i = 0; i < (int) (x); i++)
#define REPS(i, x) for (int i = 1; i <= (int) (x); i++)
#define RREP(i, x) for (int i = ((int) (x) -1); i >= 0; i--)
#define RREPS(i, x) for (int i = ((int) (x)); i > 0; i--)
#define ALL(x) ((x).begin(), (x).end())
#define SIZE(x) ((int) (x).size())
#define BITS(x) (1LL << (x))

constexpr int INF = 1001001001;
constexpr ll LINF = 1001001001001001001LL;
constexpr int MOD = 1000000007;
constexpr double EPS = 1e-10;
constexpr double PI = 3.141592653589793;
constexpr int dx[4] = {1, 0, -1, 0};
constexpr int dy[4] = {0, 1, 0, -1};
constexpr int dx8[8] = {1, 1, 1, 0, 0, -1, -1, -1};
constexpr int dy8[8] = {1, 0, -1, 1, -1, 1, 0, -1};

random_device seed_gen;
mt19937 mrand(seed_gen());
mt19937_64 mrand64(seed_gen());
int rand32(int x) {
	return mrand() % x;
}
ll rand64(long x) {
	return mrand64() % x;
}

template<typename A, typename B> ostream& operator<<(ostream& out, const pair<A, B>& a) {
	out << "(" << a.first << "," << a.second << ")";
	return out;
}
template<typename T, size_t N> ostream& operator<<(ostream& out, const array<T, N>& a) {
	out << "[";
	bool first = true;
	for (auto& v : a) {
		out << (first ? "" : ",");
		out << v;
		first = 0;
	}
	out << "]";
	return out;
}
template<typename T> ostream& operator<<(ostream& out, const vector<T>& a) {
	out << "[";
	bool first = true;
	for (auto& v : a) {
		out << (first ? "" : ",");
		out << v;
		first = 0;
	}
	out << "]";
	return out;
}
template<typename T, class Cmp> ostream& operator<<(ostream& out, const set<T, Cmp>& a) {
	out << "{";
	bool first = true;
	for (auto& v : a) {
		out << (first ? "" : ",");
		out << v;
		first = 0;
	}
	out << "}";
	return out;
}
template<typename U, typename T, class Cmp> ostream& operator<<(ostream& out, const map<U, T, Cmp>& a) {
	out << "{";
	bool first = true;
	for (auto& p : a) {
		out << (first ? "" : ",");
		out << p.first << ": " << p.second;
		first = 0;
	}
	out << "}";
	return out;
}
#ifdef LOCAL
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
#else
#define trace(...) 42
#endif
template<typename Arg1> void __f(const char* name, Arg1&& arg1) {
	cerr << name << ": " << arg1 << endl;
}
template<typename Arg1, typename... Args> void __f(const char* names, Arg1&& arg1, Args&&... args) {
	const char* comma = strchr(names + 1, ',');
	cerr.write(names, comma - names) << ": " << arg1 << " |";
	__f(comma + 1, args...);
}

struct fast_ios {
	static constexpr int IOS_PREC = 15;
	static constexpr bool AUTOFLUSH = false;

	fast_ios() {
		cin.tie(nullptr);
		ios::sync_with_stdio(false);
		cout << fixed << setprecision(IOS_PREC);
		if (AUTOFLUSH) cout << unitbuf;
	}
} fast_ios_;

void dfs(int x, int y, int s[][55], const int& h, const int& w) {
	s[y][x] = 0;
	for (int i = 0; i < 8; i++) {
		int nx = x + dx8[i];
		int ny = y + dy8[i];
		if (nx < 0 || ny < 0 || nx >= w || ny >= h || !s[ny][nx]) continue;
		dfs(nx, ny, s, h, w);
	}
}

int main() {
	while (true) {
		int h, w;
		cin >> w >> h;
		if (h == 0 && w == 0) break;
		int s[55][55];
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				cin >> s[i][j];
			}
		}
		int ans = 0;
		for (int i = 0; i < h; i++) {
			for (int j = 0; j < w; j++) {
				if (s[i][j]) {
					dfs(j, i, s, h, w);
					ans++;
				}
			}
		}
		cout << ans << endl;
	}
	return 0;
}