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 <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <complex>
#include <cstdlib>
#include <cstring>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <functional>
  
#define mp       make_pair
#define pb       push_back
#define all(x)   (x).begin(),(x).end()
#define rep(i,n) for(int i=0;i<(n);i++)
  
using namespace std;
  
typedef    long long          ll;
typedef    unsigned long long ull;
typedef    vector<bool>       vb;
typedef    vector<int>        vi;
typedef    vector<vb>         vvb;
typedef    vector<vi>         vvi;
typedef    pair<int,int>      pii;
  
const int INF=1<<29;
const double EPS=1e-9;
  
const int dx[]={1,0,-1,0,1,1,-1,-1},dy[]={0,-1,0,1,1,-1,-1,1};

bool ok(std::vector<vector<int> > &map, int x, int y) {
    int H = map.size();
    int W = map[0].size();
    if (x < 0 || x >= W || y < 0 || y >= H) return false;
    return true;
}

void color(std::vector<vector<int> > &map, int i, int j) {
    if (map[i][j] == -1) return;
    map[i][j] = -1;

    for (int k = 0; k < 8; k++) {
        int px = j + dx[k];
        int py = i + dy[k];
        if (!ok(map, px, py)) continue;
        if (map[py][px] == 0) continue;
        if (map[py][px] == 1) {
            color(map, py, px);
        }
    }
}

int main(int argc, char const *argv[]) {
    int W, H;
    while(cin >> W >> H) {
        if (W == 0 && H == 0) break;
        std::vector<vector<int> > map(H, vector<int>(W, 0));
        for (int i = 0; i < H; i++) {
            for (int j = 0; j < W; j++) {
                cin >> map[i][j];
            }
        }
        int count = 0;
        for (int i = 0; i < H; i++) {
            for (int j = 0; j < W; j++) {
                if (map[i][j] == 1) {
                    count++;
                    color(map, i, j);
                }
            }
        }
        cout << count << endl;
    }
    return 0;
}

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

using namespace std;

typedef pair<int, int> pii;

int field[52][52];

int main(){
	while(true){
		int w, h;
		cin >> w >> h;
		if(w == 0 && h == 0){ break; }
		for(int x = 0; x <= w + 1; ++x){ field[0][x] = field[h + 1][x] = 0; }
		for(int y = 1; y <= h; ++y){
			field[y][0] = field[y][w + 1] = 0;
			for(int x = 1; x <= w; ++x){ cin >> field[y][x]; }
		}
		int answer = 0;
		for(int y = 1; y <= h; ++y){
			for(int x = 1; x <= w; ++x){
				if(field[y][x] == 0){ continue; }
				++answer;
				std::stack<pii> stk;
				stk.push(pii(x, y));
				while(!stk.empty()){
					pii pt = stk.top();
					stk.pop();
					if(field[pt.second][pt.first] > 0){
						field[pt.second][pt.first] = 0;
						stk.push(pii(pt.first - 1, pt.second - 1));
						stk.push(pii(pt.first - 1, pt.second));
						stk.push(pii(pt.first - 1, pt.second + 1));
						stk.push(pii(pt.first, pt.second - 1));
						stk.push(pii(pt.first, pt.second + 1));
						stk.push(pii(pt.first + 1, pt.second - 1));
						stk.push(pii(pt.first + 1, pt.second));
						stk.push(pii(pt.first + 1, pt.second + 1));
					}
				}
			}
		}
		cout << answer << endl;
	}
	return 0;
}

C++: // 2013/07/05 Tazoe

#include <iostream>
using namespace std;

void DFS(int M[52][52], int y, int x)
{
	M[y][x] = 0;

	if(M[y-1][x]==1)
		DFS(M, y-1, x);
	if(M[y-1][x+1]==1)
		DFS(M, y-1, x+1);
	if(M[y][x+1]==1)
		DFS(M, y, x+1);
	if(M[y+1][x+1]==1)
		DFS(M, y+1, x+1);
	if(M[y+1][x]==1)
		DFS(M, y+1, x);
	if(M[y+1][x-1]==1)
		DFS(M, y+1, x-1);
	if(M[y][x-1]==1)
		DFS(M, y, x-1);
	if(M[y-1][x-1]==1)
		DFS(M, y-1, x-1);
}

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

		if(w==0 && h==0)
			break;

		int M[52][52];
		for(int y=0; y<h+2; y++){
			for(int x=0; x<w+2; x++){
				M[y][x] = 0;
			}
		}

		for(int y=1; y<=h; y++){
			for(int x=1; x<=w; x++){
				cin >> M[y][x];
			}
		}

		int cnt = 0;

		for(int y=1; y<=h; y++){
			for(int x=1; x<=w; x++){
				if(M[y][x]==1){
					cnt++;
					DFS(M, y, x);
				}
			}
		}

		cout << cnt << endl;
	}

	return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;

int main(){
    do{
        long long w, h;
        cin >> w >> h;
        if(w == 0)break;
        
        vector<vector<int>> c(h + 2, vector<int>(w + 2));
        for(int i = 0; i < h; ++i){
            for(int j = 0; j < w; ++j){
                cin >> c[i + 1][j + 1];
            }
        }
        
        queue<pair<int, int>> q;
        constexpr int move[9] = {0, 1, 1, -1, 0, -1, -1, 1};
        
        long long ans = 0;
        
        for(int i = 1; i <= h; ++i){
            for(int j = 1; j <= w; ++j){
                if(c[i][j]){
                    ++ans;
                    
                    q.emplace(i, j);
                    c[i][j] = false;
                    
                    while(!q.empty()){
                        auto t = q.front();
                        q.pop();
                        for(int i = 0; i < 8; ++i){
                            int y = t.first + move[i];
                            int x = t.second + move[i + 1];
                            if(c[y][x]){
                                q.emplace(y, x);
                                c[y][x] = false;
                            }
                        }
                    }
                    
                }
            }
        }
        
        cout << ans << endl;
        
    }while(true);
    
    return 0;
}