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>
#define r(i,n) for(int i = 0; i<n; i++)
typedef long long ll;
using namespace std;
typedef pair<int,int> P;

int w,h,sum=0,umi[52][52];

int kesi(int a,int b){
  umi[a][b]=0;
  for(int dx=-1;dx<=1;dx++){
    for(int dy=-1;dy<=1;dy++){
      if(umi[a+dx][b+dy]==1){
        kesi(a+dx,b+dy);
      }
    }
  }
  return 0;
}

int main(){
  while(cin >> w >> h&&w&&h){
    r(i,h){
      r(j,w){
        cin >> umi[i][j];
      }
    }
    r(i,h){
      r(j,w){
        if(umi[i][j]==1){
          sum++;
          kesi(i,j);
        }
      }
    }
    cout<<sum<<endl;
    sum=0;
  }
}

C++: #include<iostream>
#include<fstream>

using namespace std;

	ifstream fin;
	ofstream fout;

	//http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=1160&lang=jp

	int gomi = 0;

	int a[52][52] = {};
	void check(int, int);

	int main(){

		fin.open("input.txt");
		fout.open("output.txt");

		int width = 0, height = 0;
		int count = 0;

		while (true){

			cin >> width >> height;
			if (width == 0 && height == 0)break;

			//初期化
			count = 0;
			for (int i = 0; i < 50; i++)
				for (int j = 0; j < 50; j++)
					a[i + 1][j + 1] = 0;

			for (int i = 0; i < height; i++)
				for (int j = 0; j < width; j++)
					cin >> a[i + 1][j + 1];

			for (int i = 0; i < height; i++){
				for (int j = 0; j < width; j++){
					if (a[i + 1][j + 1] == 1){
						check(i + 1, j + 1);
						count++;
					}
				}
			}
			cout << count << endl;
			fout << count << endl;
		}
	}

	void check(int y, int x){
		for (int i = -1; i <= 1; i++)
			for (int j = -1; j <= 1; j++)
				if (i + j != 0 || i - j != 0)
					if (a[y + i][x + j] == 1){
			a[y + i][x + j] = 0;
			check(y + i, x + j);
					}
	}
//------------------------------------------------------------↑↓どちらでもいい------------------------------------------------------------
/*	void check(int y, int x){
		if (a[y + 1][x] == 1){
			a[y + 1][x] = 0;
			check(y + 1, x);
		}
		//-----------------------------
		if (a[y][x + 1] == 1){
			a[y][x + 1] = 0;
			check(y, x + 1);
		}
		//-----------------------------
		if (a[y - 1][x] == 1){
			a[y - 1][x] = 0;
			check(y - 1, x);
		}
		//-----------------------------
		if (a[y][x - 1] == 1){
			a[y][x - 1] = 0;
			check(y, x - 1);
		}
		//-----------------------------
		if (a[y + 1][x + 1] == 1){
			a[y + 1][x + 1] = 0;
			check(y + 1, x + 1);
		}
		//-----------------------------
		if (a[y + 1][x - 1] == 1){
			a[y + 1][x - 1] = 0;
			check(y + 1, x - 1);
		}
		//-----------------------------
		if (a[y - 1][x + 1] == 1){
			a[y - 1][x + 1] = 0;
			check(y - 1, x + 1);
		}
		//-----------------------------
		if (a[y - 1][x - 1] == 1){
			a[y - 1][x - 1] = 0;
			check(y - 1, x - 1);
		}
		//-----------------------------
	}*/

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

void search(int i,int j,int **c,int h,int w){
  c[i][j] = 0;
  if(j<w-1 && c[i][j+1]==1) search(i,j+1,c,h,w);
  if(i<h-1 && c[i+1][j]==1) search(i+1,j,c,h,w);

  if(j>0 && i<h-1 && c[i+1][j-1]==1) search(i+1,j-1,c,h,w);
  if(j<w-1 && i>0 && c[i-1][j+1]==1) search(i-1,j+1,c,h,w);
  if(j>0 && i>0 && c[i-1][j-1]==1) search(i-1,j-1,c,h,w);
  if(j<w-1 && i<h-1 && c[i+1][j+1]==1) search(i+1,j+1,c,h,w);
  if(i>0 && c[i-1][j]==1) search(i-1,j,c,h,w);
  if(j>0 && c[i][j-1]==1) search(i,j-1,c,h,w);
}

int main(){
  vector<int> vec;
  while(1){
    int w,h;
    cin >> w >> h;
    if(w==0 && h==0) break;
    int **c = (int**)malloc(sizeof(int*)*h);
    for(int i=0;i<h;i++){
        c[i] = (int*)malloc(sizeof(int*)*w);
        for(int j=0;j<w;j++) cin >> c[i][j];
    }
    int count = 0;
    for(int i=0;i<h;i++){
      for(int j=0;j<w;j++){
        if(c[i][j]==1){
          count += 1;
          search(i,j,c,h,w);
        }
      }
    }
    //cout << count << endl;
    vec.push_back(count);
    for(int i=0;i<h;i++){
        free(c[i]);
    }
    free(c);
  }
  int n = vec.size();
  for(int i=0;i<n;i++) cout << vec[i] << endl;
  return 0;
}

C++: #include <bits/stdc++.h>

#define REP(i, n) for(int (i)=0; (i)<(n); (i)++)
#define ALL(v) (v).begin(), (v).end()
#define INF 1e9

using namespace std;
typedef pair<int, int> pii;

int w, h;
int m[50][50];
int dx[8] = {1, 1, 1, 0, 0, -1, -1, -1};
int dy[8] = {-1, 0, 1, -1, 1, -1, 0, 1};

void dfs(int nw, int nh){
  REP(i, 8){
    if(nw + dx[i] < 0 or nw + dx[i] >= w or nh + dy[i] < 0 or nh + dy[i] >= h) continue;
    if(m[nw+dx[i]][nh+dy[i]] == 1) { m[nw+dx[i]][nh+dy[i]] = 0; dfs(nw+dx[i], nh+dy[i]); }
  }
  return;
}

int main(){
  while(cin >> w >> h and w + h){
    int res = 0;
    REP(i, h) REP(j, w) cin >> m[j][i];
    REP(i, h) REP(j, w) { if(m[j][i]) { dfs(j, i); res++; } }
    cout << res << endl;
  }
  return 0;
}