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<algorithm>

using namespace std;

int field[52][52];

void DFS(int x, int y){
    if(field[x][y]==1){
        field[x][y]=-1;
        DFS(x-1,y-1);
        DFS(x,y-1);
        DFS(x+1,y-1);
        DFS(x-1,y);
        DFS(x+1,y);
        DFS(x-1,y+1);
        DFS(x,y+1);
        DFS(x+1,y+1);
    }
}


int main(){
    int w,h;
    while(cin>>w>>h){
        if(w==0&&h==0)break;
        for(int i=0; i<50; i++){
            for(int j=0; j<50; j++){
                field[i][j]=0;
            }
        }
        
        for(int i=1; i<=h; i++){
            for(int j=1; j<=w; j++){
                cin>>field[i][j];
            }
        }
        int sum=0;
        for(int i=1; i<=h; i++){
            for(int j=1; j<=w; j++){
                if(field[i][j]==1){
                    sum++;
                    DFS(i,j);
                }
            }
        }
        cout<<sum<<endl;
    }
}

C++: ///
// File:  1160.cpp
// Author: ymiyamoto
//
// Created on Sun Nov 12 16:15:22 2017
//

#include <array>
#include <cstdint>
#include <iostream>

using namespace std;

void dfs(int32_t h, int32_t w, array<array<uint32_t, 50>, 50> &arr, int32_t i, int32_t j)
{
  arr[i][j] = 0;

  for (int32_t l = -1; l <= 1; l++) {
    for (int32_t k = -1; k <= 1; k++) {
      if (0 <= i + l && i + l < h && 0 <= j + k && j + k < w) {
        if (arr[i + l][k + j] == 1) {
          dfs(h, w, arr, i + l, k + j);
        }
      }
    }
  }
}

int32_t main()
{
  while (true) {
    uint32_t w, h;
    cin >> w >> h;
    if (w == 0) break;

    array<array<uint32_t, 50>, 50> arr;
    for (uint32_t i = 0; i < h; i++) {
      for (uint32_t j = 0; j < w; j++) {
        cin >> arr[i][j];
      }
    }

    uint32_t count = 0;
    for (uint32_t i = 0; i < h; i++) {
      for (uint32_t j = 0; j < w; j++) {
        if (arr[i][j] == 1) {
          count++;
          dfs(h, w, arr, i, j);
        }
      }
    }
    cout << count << endl;
  }

  return 0;
}

C++: #include<iostream>
#include<iomanip>
#include<cmath>
#include<string>
#include<vector>
#include<list>
#include<algorithm>
#include<map>
#include<set>
#include<queue>
#include<stack>
using namespace std;
typedef long long ll;
#define fi first
#define se second
#define mp make_pair
#define rep(i, n) for(int i=0;i<n;++i)
#define rrep(i, n) for(int i=n;i>=0;--i)
const int inf=1e9+7;
const ll mod=1e9+7;
const ll big=1e18;
const double PI=2*asin(1);

int main() {
    int W, H;
    int island[55][55];
    int ans;
    vector<int> ansarr;
    queue<pair<int, int> > que;
    pair<int, int> state;
    while(true){
        cin>>W>>H;
        if((W==0) && (H==0)) break;
        for(int i=0;i<H;++i){
            for(int j=0;j<W;++j){
                cin>>island[i][j];
            }
        }
        ans = 0;
        for(int i=0;i<H;++i){
            for(int j=0;j<W;++j){
                if(island[i][j]==1){
                    ans++;
                    que.push(mp(i, j));
                    while(!que.empty()){
                        state = que.front();que.pop();
                        if(island[state.fi][state.se]==0) continue;
                        island[state.fi][state.se] = 0;
                        if((state.fi>0) && (island[state.fi-1][state.se]==1)){
                            que.push(mp(state.fi-1, state.se));
                        }
                        if((state.fi<H-1) && (island[state.fi+1][state.se]==1)){
                            que.push(mp(state.fi+1, state.se));
                        }
                        if((state.se>0) && (island[state.fi][state.se-1]==1)){
                            que.push(mp(state.fi, state.se-1));
                        }
                        if((state.se<W-1) && (island[state.fi][state.se+1]==1)){
                            que.push(mp(state.fi, state.se+1));
                        }
                        if((state.fi>0) && (state.se>0) && (island[state.fi-1][state.se-1]==1)){
                            que.push(mp(state.fi-1, state.se-1));
                        }
                        if((state.fi>0) && (state.se<W-1) && (island[state.fi-1][state.se+1]==1)){
                            que.push(mp(state.fi-1, state.se+1));
                        }
                        if((state.fi<H-1) && (state.se>0) && (island[state.fi+1][state.se-1]==1)){
                            que.push(mp(state.fi+1, state.se-1));
                        }
                        if((state.fi<H-1) && (state.se<W-1) && (island[state.fi+1][state.se+1]==1)){
                            que.push(mp(state.fi+1, state.se+1));
                        }
                    }
                }
            }
        }
        ansarr.push_back(ans);
    }
    for(int i=0;i<ansarr.size();++i){
        cout<<ansarr[i]<<endl;
    }
}

C++: #include <iostream>
#include <algorithm>
using namespace std;
int m[55][55];

void fill_(int x,int y,int i){
    if(m[x][y]!=1){
        return;
    }
    m[x][y]=i;
    for(int dx=-1;dx<=1;++dx){
        for(int dy=-1;dy<=1;++dy){
            if(dx||dy){
                fill_(x+dx,y+dy,i);
            }
        }
    }
}

int main(void){
    // Your code here!
    while(1){
        for(int i=0;i<55;++i)fill(m[i],m[i]+55,-1);
        
        
        int w,h;
        cin>>w>>h;
        if(w==0&&h==0)break;
        for(int x=0; x<h;++x){
            for(int y=0;y<w;++y){
                int t;cin>>t;
                m[x+1][y+1]=t;
            }
        }
        int res=0;
        for(int x=1;x<=h;++x){
            for(int y=1;y<=w;++y){
                if(m[x][y]==1){
                    ++res;
                    fill_(x,y,res+1);
                }
            }
        }
        cout<<res<<endl;
    }
}