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 "bits/stdc++.h"
using namespace std;

#define ul unsigned long long
#define ll long long

ll td[8][2]={{-1,-1},{-1,0},{-1,1},{0,1},{1,1},{1,0},{1,-1},{0,-1}};

void dfs(int p[50][50],ll w,ll h,ll cx,ll cy){
  if (cx < 0 || cx >= w || cy < 0 || cy >= h)
    return;
  //cout << cx << "," << cy <<":"<<(int)p[cy][cx]<< endl;
  if (p[cy][cx] == 0)
    return;
  p[cy][cx]=0;
  ll nx,ny;
  for (ll i = 0; i < 8; i++)
  {
    nx = cx + td[i][0];
    ny = cy + td[i][1];
    dfs(p,w,h,nx,ny);
  }
}

int main()
{
  ll w,h;
  int p[50][50];
  ul ct = 0;

  cin >> w >> h;
  while (w | h)
  {
    ct=0;
    for (ll i = 0; i < h; i++)
    {
      for (ll j = 0; j < w; j++)
      {
        cin >> p[i][j];
      }
    }

    for (ll i = 0; i < h; i++)
    {
      for (ll j = 0; j < w; j++)
      {
        if (p[i][j])
          ct++;
        dfs(p, w, h, j, i);
      }
    }
    cout << ct << endl;
    cin >> w >> h;
  }

  return 0;
}

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

const int dx[3]={-1,0,1};

int w,h,ans;
queue<pair<int,int>> que;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    while(cin >> w >> h,w){
        vector<vector<int>> m(h,vector<int>(w));
        for (int i=0;i<h;++i)
            for (int j=0;j<w;++j)
                cin >> m[i][j];
        vector<vector<int>> visited(h,vector<int>(w,0));
        ans=0;
        for (int i=0;i<h;++i){
            for (int j=0;j<w;++j){
                if (visited[i][j]||!m[i][j]) continue;
                ++ans;
                visited[i][j]=1; que.emplace(i,j);
                while(!que.empty()){
                    pair<int,int> p=que.front(); que.pop();
                    for (int k=0;k<3;++k){
                        for (int l=0;l<3;++l){
                            int nh=p.first+dx[k],nw=p.second+dx[l];
                            if (nh<0||h<=nh||nw<0||w<=nw) continue;
                            if (visited[nh][nw]||!m[nh][nw]) continue;
                            visited[nh][nw]=1; que.emplace(nh,nw);
                        }
                    }
                }
            }
        }
        cout << ans << endl;
    }
}

C++: #include<iostream>
#include<algorithm>
#include<vector>
#include<stdio.h>
#include<cstring>
#include<math.h>
#include<map>
#include<bitset>
#include<iomanip>
using namespace std;

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
int w, h;
int m[50][50];
int visited[50][50] = {0};

void dfs(int x, int y) {
  visited[x][y] = 1;
  for(int i = -1; i <= 1; i++) {
    for(int j = -1; j <= 1; j++) {
      int nx = x + i;
      int ny = y + j;
      if(0 <= nx && nx < h && 0 <= ny && ny < w && visited[nx][ny] == 0 && m[nx][ny] == 1) {
        dfs(nx, ny);
      }
    }
  }
  
}

int main() {
  while(true) {
    rep(i, h) {
      rep(j, w) {
        visited[i][j] = 0;
      }
    }
    cin >> w >> h;
    if(w == 0 && h == 0) break;
    rep(i, h) {
      rep(j, w) {
        cin >> m[i][j];
      }
    }
    int count = 0;
    for(int i = 0; i < h; i++) {
      for(int j = 0; j < w; j++) {
        if(m[i][j] == 1 && visited[i][j] == 0) {
          count++;
          dfs(i, j);
        }
      }
    }
    cout << count << endl;
  }
  return 0;
}

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

int H, W;
bool grid[55][55];

void island(int h, int w) {
  grid[h][w] = 0;

  for(int i = -1; i <= 1; ++i) {
    for(int j = -1; j <= 1; ++j) {
      if(i == 0 && j == 0) continue;
      int nh = h + i;
      int nw = w + j;
      if(0 <= nh && nh < H && 0 <= nw && nw < W && grid[nh][nw]) island(nh, nw);
    }
  }
}

int main(){
  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 >> grid[i][j];

    int ans = 0;
    for(int i=0; i < H; ++i) {
      for(int j=0; j < W; ++j) {
        if(grid[i][j]) {
          island(i,j);
          ++ans;
        }
      }
    }
    cout << ans << '\n';
  }

  return 0;
}

C++: #include <algorithm>
#include<iostream>
#include<vector>
#include<list>
#include<map>
#include<set>
#include<string>

#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<limits.h>

using namespace std;

long mapp[51][51];
bool seen[51][51];
int W,H;

// 八方向への移動ベクトル
const int dx[8] = {1, 0, -1, 0, -1, 1 ,-1, 1};
const int dy[8] = {0, 1, 0, -1, -1,-1 , 1, 1};

void dfs(int w,int h){

  seen[h][w] = true;
  int ii,jj;
  int nx,ny;

  for(ii=0;ii<8;ii++){

    nx = w + dx[ii];
    ny = h + dy[ii];

    if(nx < 0 || ny < 0 || nx >= W || ny >= H){continue;}
    if(mapp[ny][nx] == 0){continue;}
    if(seen[ny][nx] == true){continue;}

    //cout << "H:" << H << "W:" << W << "nx:" << nx << "ny:" << ny << endl;
    dfs(nx,ny);
  }

  
}

int main(){

  long ii,jj,kk;
  vector<int> ret;


  while(true){
    cin >> W >> H;
    //cout << "W:" << W << "H:" << H <<endl;
    if(W == 0){
      break;
    }
    memset(mapp,0,sizeof(mapp));    
    for(ii=0;ii<H;ii++){
      for(jj=0;jj<W;jj++){
        cin >> mapp[ii][jj];
      }
    }

    memset(seen,0,sizeof(seen));

    int cnt=0;

    for(ii=0;ii<H;ii++){
      for(jj=0;jj<W;jj++){

        //cout << "ii:" << ii << "jj:" << jj << endl;
        if(mapp[ii][jj] == 1 && seen[ii][jj] == false){
          //cout << "ii:" << ii << "jj:" << jj << endl;
          dfs(jj,ii);
          cnt++;
        }
      }
    }

    cout << cnt << endl;
  }
  
  return 0;
}