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 <stack>

using namespace std;

#define PAIR pair<int, int>

int main() {
	int w, h;
	while (cin >> w >> h, w != 0 && h != 0) {
		bool field[52][52] = {{false}};

		for (int i = 1; i <= h; i++) {
			for (int j = 1; j <= w; j++) {
				cin >> field[i][j];
			}
		}

		stack<PAIR> st;
		int island = 0;
		int dx[] = {0, 1, 1, 1, 0, -1, -1, -1};
		int dy[] = { -1, -1, 0, 1, 1, 1, 0, -1};

		for (int i = 1; i <= h; i++) {
			for (int j = 1; j <= w; j++) {
				if (field[i][j]) {
					st.push(PAIR(i, j));
					while (!st.empty()) {
						int x = st.top().first;
						int y = st.top().second;
						st.pop();
						field[x][y] = false;
						for (int k = 0; k < 8; k++) {
							int nextX = x + dx[k];
							int nextY = y + dy[k];
							if (field[nextX][nextY]) {
								st.push(PAIR(nextX, nextY));
							}
						}
					}
					island++;
				}
			}
		}
		cout << island << endl;
	}
}

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

char c[102][102];

int mx, my;

void dfs(int x, int y){
    if(x < 0 || y < 0 || x >= mx || y >= my){
        return;
    }
    if(c[x][y] == '0'){
        return;
    }
    c[x][y] = '0';
    dfs(x+1, y);
    dfs(x+1, y+2);
    dfs(x+1, y-2);
    dfs(x-1, y);
    dfs(x-1, y+2);
    dfs(x-1, y-2);
    dfs(x, y+2);
    dfs(x, y-2);
    return;
}

int main(){
    int W, H, cnt = 0;
    scanf("%d %d\n", &W, &H);
    while(W != 0 || H != 0){
        mx = H;
        my = 2 * W;
        for(int k = 0; k < H; k++){
            cin.getline(c[k], sizeof(c[k]));
        }
        for(int i = 0; i < H; i++){
            for(int j = 0; j < 2 * W; j++){
                if(c[i][j] == '1'){
                    cnt++;
                    dfs(i, j);
                }
            }
        }
        cout << cnt << endl;
        scanf("%d %d\n", &W, &H);
        cnt = 0;
    }
}

C++: #include <iostream>
#include <algorithm>
#include <queue>
#include <array>
using namespace std;
typedef pair<int,int> P;

const array<int,8> dx={0,1,0,-1,1,1,-1,-1};
const array<int,8> dy={1,0,-1,0,1,-1,-1,1};
const int W=50;
const int H=50;

char M[H+1][W+1];

inline bool in_M(const int y,const int x){
    return (y>=0 && y<H && x>=0 && x<W);
}

void bfs(const int sy,const int sx){
    queue<P> que;

    que.push(P(sy,sx));
    M[sy][sx]='0';

    while(!que.empty()){
        P p=que.front();que.pop();

        for(int i=0;i<dx.size();i++){
            int ddy=p.first+dy[i],ddx=p.second+dx[i];
            if(in_M(ddy,ddx) && M[ddy][ddx]=='1'){
                que.push(P(ddy,ddx));
                M[ddy][ddx]='0';
            }
        }
    }
}

void solve(){
    int sum;
    int w,h;

    while(cin>>w>>h,w|h){
        cin.ignore();
        sum=0;

        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                cin>>M[i][j];
                cin.ignore();
            }
        }

        for(int i=0;i<h;i++){
            for(int j=0;j<w;j++){
                if(M[i][j]=='1'){
                    bfs(i,j);
                    sum++;
                }
            }
        }

        cout<<sum<<endl;
    }
}

int main(){
    solve();
    return 0;
}

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

constexpr int MAX_H = 55;
constexpr int MAX_W = 55;

int H, W;
int grid[MAX_H][MAX_W];
bool reached[MAX_H][MAX_W];

#define OCTAS
#ifdef OCTAS
constexpr int dh[]{-1, -1, -1, 0, 0, +1, +1, +1};
constexpr int dw[]{-1, 0, +1, -1, +1, -1, 0, +1};
#else
constexpr int dh[]{-1, 0, 0, +1};
constexpr int dw[]{0, -1, +1, 0};
#endif

void dfs(int h, int w) {
  reached[h][w] = true;

  for (int i{}; i < sizeof(dh) / sizeof(int); ++i) {
    int nh = h + dh[i];
    if (nh < 0 || nh >= H)
      continue;
    int nw = w + dw[i];
    if (nw < 0 || nw >= W)
      continue;
    if (grid[nh][nw] == 0 || reached[nh][nw])
      continue;
    dfs(nh, nw);
  }
}

int main() {
  while (true) {
    cin >> H >> W;
    if (H == 0 && W == 0)
      break;
    for (int h{}; h < H; ++h) {
      for (int w{}; w < W; ++w) {
        reached[h][w] = false;
        cin >> grid[h][w];
      }
    }

    int island{};
    for (int h{}; h < H; ++h) {
      for (int w{}; w < W; ++w) {
        if (grid[h][w] == 0 || reached[h][w])
          continue;
        dfs(h, w);
        ++island;
      }
    }

    cout << island << endl;
  }

  return 0;
}

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

constexpr int MAX_H = 50;
constexpr int MAX_W = 50;

int H, W;
char grid[MAX_H][MAX_W];
bool reached[MAX_H][MAX_W];

#define OCTAS
#ifdef OCTAS
constexpr int dh[]{-1, -1, -1, 0, 0, +1, +1, +1};
constexpr int dw[]{-1, 0, +1, -1, +1, -1, 0, +1};
#else
constexpr int dh[]{-1, 0, 0, +1};
constexpr int dw[]{0, -1, +1, 0};
#endif

void dfs(int h, int w) {
  reached[h][w] = true;

  for (int i{}; i < sizeof(dh) / sizeof(int); ++i) {
    int nh = h + dh[i];
    if (nh < 0 || nh >= H)
      continue;
    int nw = w + dw[i];
    if (nw < 0 || nw >= W)
      continue;
    if (grid[nh][nw] == '0' || reached[nh][nw])
      continue;
    dfs(nh, nw);
  }
}

int main() {
  while (true) {
    cin >> H >> W;
    if (H == 0 && W == 0)
      break;
    fill(reached[0], reached[0] + MAX_H * MAX_W, false);
    for (int h{}; h < H; ++h) {
      for (int w{}; w < W; ++w) {
        cin >> grid[h][w];
      }
    }

    int island{};
    for (int h{}; h < H; ++h) {
      for (int w{}; w < W; ++w) {
        if (grid[h][w] == '0' || reached[h][w])
          continue;
        dfs(h, w);
        ++island;
      }
    }

    cout << island << endl;
  }

  return 0;
}