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 <bits/stdc++.h>
using namespace std;
using Graph = vector<vector<int>>;

vector<int> dx = {-1, -1, -1, 0, 1, 1, 1, 0};
vector<int> dy = {-1, 0, 1, 1, 1, 0, -1, -1}; 
int w, h;
int seen[55][55];

void dfs(const Graph &G, int x, int y){
    seen[y][x] = 1;
    for(int i = 0; i < 8; i++){
        if(x + dx[i] < 0 || x + dx[i] >= w || y + dy[i] < 0 || y + dy[i] >= h || G[y + dy[i]][x + dx[i]] == 0) continue;
        if(seen[y + dy[i]][x + dx[i]] == 1) continue;
        dfs(G, x + dx[i], y + dy[i]);
    }
}

int main(){
    while(true){
        cin >> w >> h;
        if(w == 0 && h == 0) break;
        Graph G(h);
        for(int i = 0; i < h; i++){
            for(int j = 0; j < w; j++){
                int k; cin >> k;
                G[i].push_back(k);
            }
        }
        for(int i = 0; i < 55; i++){
          for(int j = 0; j < 55; j++){
            seen[i][j] = 0;
          }
        }
        int cnt = 0; 
        for(int l = 0; l < h; l++){
            for(int m = 0; m < w; m++){
                if(G[l][m] == 1 && seen[l][m] == 0){
                    dfs(G, m, l);
                    cnt++;
                }
            }
        }
        cout << cnt << endl;
    }
}

C++: #include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <vector>
#include <map>
#include <set>
using namespace std;

struct UnionFind {
        int n;
        vector<int> parent;
        vector<int> rank;
        vector<int> num;
        int find(int x) {
                if (parent[x] == x) return  x;
                return parent[x] = find(parent[x]);
        }
        UnionFind(int n_) {
                n = n_;
                parent.resize(n);
                for (int i = 0; i < n; i ++) parent[i] = i;
                rank.assign(n, 0);
                num.assign(n, 1);
        }
        void unite(int x, int y) {
                if ((x = find(x)) != (y = find(y))) {
                        if (rank[x] < rank[y]) {
                                parent[x] = y;
                                num[y] += num[x];
                        } else {
                                parent[y] = x;
                                if (rank[x] == rank[y]) rank[x] ++;
                                num[x] += num[y];
                        }
                        n --;
                }
        }
        bool same(int x, int y) { return find(x) == find(y); }
        int get() { return n; }
        int get(int x) { return num[find(x)]; }
};

int main() {
        int w, h;
        while (scanf("%d%d", &w, &h), w) {
                vector<vector<int>> s(h, vector<int> (w));
                int lands = 0;
                map<pair<int, int>, int> ptol;
                for (int i = 0; i < h; i ++) {
                        for (int j = 0; j < w; j ++){
                                scanf("%d", &s[i][j]);
                                if (s[i][j]) {
                                        ptol[make_pair(i, j)] = lands;
                                        lands ++;
                                }
                        }
                }
                UnionFind uf(lands);
                for (int i = 0; i < h; i ++) {
                        for (int j = 0; j < w; j ++) {
                                if (s[i][j]) {
                                        if (i - 1 >= 0 && j + 1 < w && s[i - 1][j + 1]) uf.unite(ptol[make_pair(i, j)], ptol[make_pair(i - 1, j + 1)]);
                                        if (j + 1 < w && s[i][j + 1]) uf.unite(ptol[make_pair(i, j)], ptol[make_pair(i, j + 1)]);
                                        if (i + 1 < h && j + 1 < w && s[i + 1][j + 1]) uf.unite(ptol[make_pair(i, j)], ptol[make_pair(i + 1, j + 1)]);
                                        if (i + 1 < h && s[i + 1][j]) uf.unite(ptol[make_pair(i, j)], ptol[make_pair(i + 1, j)]);
                                }
                        }
                }
                printf("%d\n", uf.get());
        }
        return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
using ll=long long;
typedef pair<int,int> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
int w,h;
int nx,ny;
void dfs(vector<vector<int>> &G,int a,int b){
    G.at(a).at(b)=0;
    
    for(int k=-1;k<=1;k++){
        for(int s=-1;s<=1;l++){
            nx=a+k;
            ny=b+s;
        if(0<=nx&& nx<h && 0<=ny&& ny<w && G.at(nx).at(ny)==1) dfs(G,nx,ny);
        }
    }
    return ;
}



int main(){
    int w,h;
    cin>>w>>h;
    vector<vector<int>>G(h,vector<int>(w));
    for(int i=0;i<h;i++){
        for(int j=0;j<w;j++){
            cin>>G.at(i).at(j);
        }
    }
    int count=0;
    for(int i=0;i<h;i++){
        for(int j=0;j<w;j++){
            if(G.at(i).at(j)==1){
                dfs(G,i,j);
                count++;
            }
        }
    }
cout<<count<<endl;
}

C++: #include <algorithm>
#include <cmath>
#include <climits>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <fstream>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <vector>
#include <cassert>

using namespace std;

#define LOG(...) printf(__VA_ARGS__)
//#define LOG(...)
#define FOR(i,a,b) for(int i=(int)(a);i<(int)(b);++i)
#define REP(i,n) for(int i=0;i<(int)(n);++i)
#define ALL(a) (a).begin(),(a).end()
#define RALL(a) (a).rbegin(),(a).rend()
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define RSORT(c) sort((c).rbegin(),(c).rend())
#define CLR(a) memset((a), 0 ,sizeof(a))

typedef long long ll;
typedef unsigned long long ull;
typedef vector<bool> vb;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<vb> vvb;
typedef vector<vi> vvi;
typedef vector<vll> vvll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;

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

const int L_MAP = 50;
bool field[L_MAP + 2][L_MAP + 2];

const bool LAND = true;
const bool SEA = false;

void dfs(int x, int y){
    if(field[y][x] == SEA)
        return;

    field[y][x] = SEA;
    FOR(dy, -1, 1 + 1){
        FOR(dx, -1, 1 + 1){
            dfs(x+ dx, y + dy);
        }
    }
}

int main() {
    int w, h;
    while(cin >> w >> h, w|h){
        fill_n((bool *)field, (L_MAP + 2) * (L_MAP + 2), SEA);
        REP(y, h){
            REP(x, w) {
                cin >> field[y][x];
            }
        }

        int cnt = 0;
        REP(y, h + 1) {
            REP(x, w + 1) {
                if (field[y][x] == LAND) {
                    dfs(x, y);
                    cnt ++;
                }
            }
        }

        cout << cnt << endl;
    }

}