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 <stdio.h>
int map[100][100],n,m;
bool went[100][100];
void walk(int x,int y){
    if(x<0||y<0||x>=n||y>=m)return ;
    if(went[x][y])return ;
    if(map[x][y]==0)return ;
    went[x][y]=true;
    walk(x-1,y);
    walk(x+1,y);
    walk(x,y+1);
    walk(x,y-1);
    walk(x+1,y+1);
    walk(x+1,y-1);
    walk(x-1,y+1);
    walk(x-1,y-1);
    return ;
}
int main(){
    int ans;
    while(1){
        scanf("%d%d",&m,&n);
        if(n==0&&m==0)return 0;
        ans=0;
        for(int i=0;i<n;i++)for(int j=0;j<m;j++){
            scanf("%d",&map[i][j]);
            went[i][j]=false;
        }
        for(int i=0;i<n;i++)for(int j=0;j<m;j++)if(!went[i][j]&&map[i][j]==1){
            ans++;
            walk(i,j);
        }
        printf("%d\n",ans);
    }
}

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

using namespace std;


bool done[52][52];
int field[52][52];
int ofs[8][2] = {
  {0, 1},
  {1, 0},
  {-1, 0},
  {0, -1},
  {1, 1},
  {1, -1},
  {-1,-1},
  {-1, 1}
};

void paint(int y, int x)
{
  for (int i = 0; i < 8; ++i) {
    int nx = x + ofs[i][0];
    int ny = y + ofs[i][1];
    if (field[ny][nx] && !done[ny][nx]) {
      done[ny][nx] = true;
      paint(ny, nx);
    }
  }
}

int main() {
  int w, h;
  for(;;) {
    cin >> w >> h;
    if ((w|h) == 0) {
      break;
    }
    memset(field, 0, sizeof(field));
    memset(done, 0, sizeof(done));
    for (int i = 1; i <= h; ++i) {
      for (int j = 1; j <= w; ++j) {
        cin >> field[i][j];
      }
    }
    int cnt = 0;
    for (int i = 1; i <= h; ++i) {
      for (int j = 1; j <= w; ++j) {
        if (field[i][j] && !done[i][j]) {
          paint(i, j);
          ++cnt;
        }
      }
    }
    cout << cnt << endl;
  }
  return 0;
}