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++: #include<iostream>
#include<vector>
#include<stack>
using namespace std;

typedef long long itemType;

struct node
{long long v; struct node *next;};

void visit(stack<long long> stack, long long k, struct node *z, struct node **adj, long long id, long long val[]){
    struct node *t;
    t = new node;
    stack.push(k);
    while(!stack.empty()){
        k = stack.top();
        stack.pop();
        val[k] = ++id;
        for(t = adj[k]; t != z; t = t -> next){
            if(val[t -> v] == 0){
                stack.push(t -> v);
                val[t -> v] = -1;
            }
        }
    }
}

void search(stack<long long>stack, long long V, struct node *z, struct node **adj, long long id, long long val[], long long &comp, vector<vector<bool> > c, long long w){
    long long k;
    for(k = 1; k <= V; k++) val[k] = 0;
    for(k = 1; k <= V; k++){
        if(val[k] == 0){
            if(c[(k-1)/w + 1][((k-1)%w) + 1]) comp++;
            visit(stack, k, z, adj, id, val);
        }
    }
}

int main(){
    long long w, h;
    vector<bool> sub;
    bool c_sub;
    long long i, j;
    for(i = 0; i <= 50; i++){
        sub.push_back(0);
    }
    vector<vector<bool> > c;
    for(i = 0; i <= 50; i++){
        c.push_back(sub);
    }
    long long V;
    struct node *z;
    z = new node;
    z -> next = z;
    struct node *adj[2501];
    struct node *t;
    long long x, y;
    while(1){

        //input
        cin >> w >> h;
        if(w == 0 && h == 0) break;
        for(i = 1; i <= h; i++){
            for(j = 1; j <= w; j++){
                cin >> c_sub;
                c[i][j] = c_sub;
            }
        }

        //adjacency list representation
        V = w * h;
        stack<long long> stack;
        for(i = 1; i <= V; i++){
            adj[i] = z;
        }
        for(j = 1; j <= w; j++){
            for(i = 1; i <= h-1; i++){
                if(c[i][j] & c[i+1][j]){
                    x = (i-1)*w + j;
                    y = i*w + j;
                    t = new node;
                    t -> v = x;
                    t -> next = adj[y];
                    adj[y] = t;
                    t = new node;
                    t -> v = y;
                    t -> next = adj[x];
                    adj[x] = t;
                    
                }
            }
        }
        
        for(i = 1; i <= h; i++){
            for(j = 1; j <= w-1; j++){
                if(c[i][j] & c[i][j+1]){
                    x = (i-1)*w + j;
                    y = (i-1)*w + j+1;
                    t = new node;
                    t -> v = x;
                    t -> next = adj[y];
                    adj[y] = t;
                    t = new node;
                    t -> v = y;
                    t -> next = adj[x];
                    adj[x] = t;
                    
                }
            }
        }
        for(i = 1; i <= h-1; i++){
            for(j = 1; j <= w-1; j++){
                if(c[i][j] & c[i+1][j+1]){
                    x = (i-1)*w + j;
                    y = i*w + j+1;
                    t = new node;
                    t -> v = x;
                    t -> next = adj[y];
                    adj[y] = t;
                    t = new node;
                    t -> v = y;
                    t -> next = adj[x];
                    adj[x] = t;
                    
                }
            }
        }
        for(i = 1; i <= h-1; i++){
            for(j = 1; j <= w-1; j++){
                if(c[i+1][j] & c[i][j+1]){
                    x = i*w + j;
                    y = (i-1)*w + j+1;
                    t = new node;
                    t -> v = x;
                    t -> next = adj[y];
                    adj[y] = t;
                    t = new node;
                    t -> v = y;
                    t -> next = adj[x];
                    adj[x] = t;
                    
                }
            }
        }

        //depth first search
        long long id = 0;
        long long val[V + 1];
        long long comp = 0;
        search(stack, V, z, adj, id, val, comp, c, w);
        cout << comp << endl;
    }

    return 0;
}

C++: #include <iostream>
#include <algorithm>

using namespace std;

int c[50][50];

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

int ret;

int w,h;

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

int main(){
	while(cin >> w >> h,w){
		ret = 0;
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				cin >> c[j][i];
			}
		}
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				if(c[i][j] == 1){
					ret++;
					dfs(j,i);
				}
			}
		}
		cout << ret << endl;
	}
	return 0;
}

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

using namespace std;

#define vec vector
#define rep(i, n) for (int i = 0; i < (int)n; i++)

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

int dp[55][55];
int c[55][55];

int check(int x, int y)
{
	if (dp[x][y]) return 0;
	if (c[x][y] == 0) return 0;
	dp[x][y] = 1;
	
	rep(i, 8) {
		int xx = x + dx[i];
		int yy = y + dy[i];
		int take = check(xx, yy);
	}
	return 1;
}

int main(void)
{
	while(1) {
		int w, h;
		cin >> w >> h;
		if (w == 0) break;
		rep(i, 55) rep(j, 55) c[i + 1][j + 1] = 0;
		rep(i, h) rep (j, w) cin >> c[i + 1][j + 1];
		rep(i, 55) rep(j, 55) dp[i][j] = 0;
		rep(i, 55) {
			dp[0][i] = 1;
			dp[i][0] = 1;
			dp[h + 1][i] = 1;
			dp[i][w + 1] = 1;
		}

		int ans = 0;
		rep(i, h) rep(j, w) if (c[i + 1][j + 1]) ans += check(i + 1, j + 1);
		cout << ans << endl;
	}
	return 0;
}