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 <iostream>
#include <queue>
#include <utility>
using namespace std;
typedef pair<int, int> P;

const int dx[4] = {1, 0, -1, 0};
const int dy[4] = {0, 1, 0, -1};

int main()
{
    while(true){
        int w, h;
        cin >> w >> h;
        if(w == 0 && h == 0) break;
        int c[53][53];
        for(int j = 0; j < w + 2; j++){
            c[0][j] = c[h + 1][j] = 0;
        }
        for(int i = 1; i <= h; i++){
            c[i][0] = c[i][w + 1] = 0;
            for(int j = 1; j <= w; j++) cin >> c[i][j];
        }
        queue<P> que;
        int ans = 0;
        for(int i = 1; i <= h; i++){
            for(int j = 1; j <= w; j++){
                if(c[i][j] == 1){
                    c[i][j] = 0;
                    que.push(P(i, j));
                    while(que.size()){
                        int x = que.front().first;
                        int y = que.front().second;
                        que.pop();
                        for(int k = x - 1; k <= x + 1; k++){
                            for(int l = y - 1; l <= y + 1; l++){
                                if(c[k][l] == 1){
                                    c[k][l] = 0;
                                    que.push(P(k, l));
                                }
                            }
                        }
                    }
                    ans++;
                }
            }
        }
        cout << ans << endl;
    }
}

C++: #include <iostream>
#include <queue>
using namespace std;

int w, h, c, n;
int a[50][50];
queue<int> q;

void bfs() {
	int x, y;
	while (1) {
		x = q.front() % w;
		y = q.front() / w;
		if ( x > 0 && a[y][x - 1] == 1 ) {
			a[y][x - 1] = 0;
			q.push( y * w + x - 1 );
		}
		if ( y > 0 && a[y - 1][x] == 1 ) {
			a[y - 1][x] = 0;
			q.push( ( y - 1 ) * w + x );
		}
		if ( x < w - 1 && a[y][x + 1] == 1 ) {
			a[y][x + 1] = 0;
				q.push( y * w + x + 1 );
		}
		if ( y < h - 1 && a[y + 1][x] == 1 ) {
			a[y + 1][x] = 0;
			q.push( ( y + 1 ) * w + x );
		}
		q.pop();
		if ( q.empty() ) break;	
	}
	n++;
}

int main() {

	while (1) {
		n = 0;
		for ( int j = 0; j < 50; j++ )
			for ( int i = 0; i < 50; i++ )
				a[j][i] = 0;
		cin >> w >> h;
		if ( w == 0 ) break;
		for ( int j = 0; j < h; j++ ) {
			for ( int i = 0; i < w; i++ ) {
				cin >> c;
				a[j][i] = c;
			}
		}
		for ( int j = 0; j < h; j++ ) {
			for ( int i = 0; i < w; i++ ) {
				if ( a[j][i] == 1 ) {
					a[j][i] = 0;
					q.push( j * w + i );
					bfs();
				}
			}
		}
		cout << n << endl;
	}
}

C++: #include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
#define coutd(n) cout << fixed << setprecision(n)
#define ll long long int
#define vl vector<ll>
#define vi vector<int>
const int INF = 2147483647;
const ll MOD = 1000000007;

using namespace std;

void dfs(const int i, const int j, const int h, const int w, const vector<vi> &grid, vector<vector<bool>> &visited) {
  if (not(0 <= i and i < h and 0 <= j and j < w))
    return;
  if (visited[i][j] or grid[i][j] == 0)
    return;
  visited[i][j] = true;
  int dx[8] = {1, 1, 0, -1, -1, -1, 0, 1};
  int dy[8] = {0, 1, 1, 1, 0, -1, -1, -1};
  REP(k, 8) { dfs(i + dx[k], j + dy[k], h, w, grid, visited); }
}

int main() {
  while (true) {
    int w, h;
    cin >> w >> h;
    if (w == 0 and h == 0)
      return 0;
    vector<vi> grid(h, vi(w, 0));
    vector<vector<bool>> visited(h, vector<bool>(w, false));
    REP(i, h) {
      REP(j, w) { cin >> grid[i][j]; }
    }

    int ans = 0;
    REP(i, h) {
      REP(j, w) {
        if (not visited[i][j] and grid[i][j] == 1) {
          ans++;
          dfs(i, j, h, w, grid, visited);
        }
      }
    }
    cout << ans << endl;
  }
  return 0;
}