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++: #pragma warning(disable:4996)
#include <bits/stdc++.h>

using namespace std;

#define REP(i,n) for (int i = 0; i<n; i++)
#define ALL(a) begin(a), end(a)
#define TPL template
#define TNM typename

using ll = long long;
using ull = unsigned long long;
TPL<TNM T> using vec = vector<T>;
TPL<TNM T> using vec2 = vec<vec<T>>;
TPL<TNM T> using vec3 = vec<vec2<T>>;
TPL<TNM T> using vec4 = vec<vec3<T>>;
TPL<TNM T> using vec5 = vec<vec4<T>>;

TPL<TNM V, TNM H> void resize(vector<V>& v, const H h) { v.resize(h); }
TPL<TNM V, TNM H, TNM ... T> inline void resize(vector<V>& v, const H& h, const T ... t) { v.resize(h); for (auto& _v : v) resize(_v, t ...); }
TPL<TNM V, TNM T> void fill(V& x, const T& val) { x = val; }
TPL<TNM V, TNM T> inline void fill(vector<V>& vec, const T& val) { for (auto& v : vec) fill(v, val); }
TPL<TNM T> inline void UNIQUE(vector<T>& vec) { sort(ALL(vec)); vec.erase(unique(ALL(vec)), vec.end()); }

class YukiIO {
	bool f = false; //改行が残っている否か
	char* buff;
	int sbuff;
	string format;
public:
	YukiIO(int s_, int pre_) { sbuff = s_; buff = new char[s_]; format = "%." + to_string(pre_) + "lf"; }
	~YukiIO() { delete buff; }
	//--------------input---------------
	inline void get(int &i_) { f = true; scanf("%d", &i_); }
	inline void get(long long &l_) { f = true; scanf("%lld", &l_); }
	inline void get(double &d_) { f = true; scanf("%lf", &d_); }
	inline void get(float &f) { f = true; scanf("%f", &f); }
	inline void get(char &c_) {
		if (f)scanf("%*c%c", &c_);
		else scanf("%c", &c_);
		f = true;
	}
	inline void get(char* s_) { f = true; scanf("%s", s_); }
	inline void get(string &s_) { f = true; scanf("%s", buff); s_ = string(buff); }
	template <typename HEAD, typename ...TAIL>inline void get(HEAD& head, TAIL& ...tails) {
		get(head);
		get(tails...);
	}
	template <typename T> inline void get(vector<T>& v_) {
		for (int i = 0; i < v_.size(); ++i) get(v_[i]);
	}
	inline void getl(string& s_) {
		if (f) { char dm; scanf("%c", &dm); }
		fgets(buff, sbuff, stdin);
		s_ = string(buff);
		f = false;
	}
	template <typename ...ARGS> inline void getf(const char* format, ARGS& ... args) {
		if (f)scanf("%*c%[^\n]", buff);
		else scanf("%[^\n]", buff);
		sscanf(buff, format, &args...);
		f = true;
	}
	//--------------outut---------------
	inline void print(bool b_) { printf("%s", b_ ? "true" : "false"); }
	inline void print(int i_) { printf("%d", i_); }
	inline void print(long long l_) { printf("%lld", l_); }
	inline void print(double d_) { printf(format.data(), d_); }
	inline void print(float f) { printf("%f", f); }
	inline void print(char c_) { printf("%c", c_); }
	inline void print(char* s_) { printf("%s", s_); }
	inline void print(string &s_) { printf("%s", s_.data()); }
	inline void print(const char* s_) { printf("%s", s_); }
	template <typename T> inline void print(vector<T>& v) {
		print(v[0]);
		for (int i = 1; i < v.size(); ++i) {
			putchar(' '); print(v[i]);
		}
	}
	inline void println() { puts(""); }
	template <typename T> inline void println(vector<T>& v) { for (int i = 0; i < v.size(); ++i) println(v[i]); }
	template <typename HEAD, typename ...TAIL>inline void print(HEAD head, TAIL ...tails) {
		print(head);
		print(tails...);
	}
	template <typename ...ARGS>inline void println(ARGS ...args) {
		print(args...);
		puts("");
	}
};

YukiIO io(114514, 12);

inline bool range1d(int x, int W) { return (x >= 0) && (W > x); }
inline bool range2d(int x, int y, int W, int H) { return (x >= 0) && (y >= 0) && (W > x) && (H > y); }
const int dx[] = { 0, 1, 0, -1, 1, -1, -1, 1 };
const int dy[] = { -1, 0, 1, 0, 1, 1, -1, -1 };

int W, H;

int dfs(vec2<int>& I, int x, int y) {
	if (I[y][x] == 0)return 0;
	I[y][x] = 0;
	REP(i, 8) {
		int nx = x + dx[i];
		int ny = y + dy[i];
		if (range2d(nx, ny, W, H)) {
			dfs(I, nx, ny);
		}
	}
	return 1;
}

int main(void) {
	while (1) {
		io.get(W, H);
		if (W + H == 0)break;
		vec2<int> I;
		resize(I, H, W);
		REP(y, H) {
			REP(x, W) {
				io.get(I[y][x]);
			}
		}
		int ans = 0;
		REP(y, H) {
			REP(x, W) {
				ans += dfs(I, x, y);
			}
		}
		io.println(ans);
	}
	return 0;
}

C++: #include <bits/stdc++.h>

using namespace std;
#define rep(i, n) for (int i = 0; i < n; i++)
#define ll long long int
#define INF 1000000007
#define llINF 1000000000000000007
#define v(i) vector<i>
#define vv(i) vector<vector<i>>
// cin.eof() 入力個数の問題
// int num = atoi(string.c_str()); 文字列の整数変換
bool visited[51][51];
int h, w;
int A[] = {1, 1, 1, 0, 0, -1, -1, -1};
int B[] = {0, 1, -1, 1, -1, 0, 1, -1};
void dfs(int x, int y, vv(int) & c) {
    if (x < 0 || x >= h || y < 0 || y >= w || c[x][y] == 0)
        return;
    if (visited[x][y])
        return;
    visited[x][y] = true;
    //cout<<"(x,y)=="<<x<<","<<y<<endl;
    rep(i, 8) {
        dfs(x + A[i], y + B[i], c);
    }
}

int main() {
   while (1) {
        cin >> w >> h;
        if(w==0 && h==0) return 0;
        vv(int) c;
        rep(i, h) {
            c.push_back({});
            rep(j, w) {
                int a;
                cin >> a;
                c[i].push_back(a);
            }
        }
        rep(i, 51) {
            rep(j, 51) {
                visited[i][j] = false;
            }
        }
        int ans = 0;
        rep(i, h) {
            rep(j, w) {
                if (visited[i][j] || c[i][j] == 0)
                    continue;
                dfs(i, j, c);
                //cout<<"dfs"<<endl;
                ans++;
            }
        }
        cout << ans << endl;
    }
    return 0;
}

C++: #include <iostream>
#include <vector>
#include <stack>

void dfs(std::vector<std::vector<int> > &map, std::stack<std::pair<int, int> > &st, int &number) {
    int dy[8] = {-1, -1, -1, 0, 0, 1, 1, 1};
    int dx[8] = {-1, 0, 1, -1, 1, -1, 0, 1};
    std::pair<int, int>  coord;
    coord.first = st.top().first;
    coord.second = st.top().second;
    map[coord.first][coord.second] = 0;
    st.pop();
    for (int i = 0; i < 8; i++) {
        if (map[coord.first + dy[i]][coord.second + dx[i]] == 1) {
            st.push(std::make_pair(coord.first + dy[i], coord.second + dx[i]));
            dfs(map, st, number);
        }
    }
    return;
}

int main(void) {
    int w;
    int h;
    int number;
    while (std::cin >> w >> h) {
        if (w == 0 && h == 0) {
            break;
        }
        std::stack<std::pair<int, int> > st;
        number = 0;
        std::vector<std::vector<int> > map(h + 2, std::vector<int>(w + 2, 0));
        for (int i = 1; i <= h; i++) {
            for (int j = 1; j <= w; j++) {
                std::cin >> map[i][j];
            }
        }
        for (int i = 1; i <= h; i++) {
            for (int j = 1; j <= w; j++) {
                if (map[i][j] == 1) {
                    st.push(std::make_pair(i, j));
                    map[i][j] = 0;
                    dfs(map, st, number);
                    number++;
                }
            }
        }
        std::cout << number << std::endl;
    }
    return 0;
}