Go: package main

import (
	"bufio"
	"container/list"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	for {
		w, h := io.NextInt(), io.NextInt()
		if w == 0 {
			break
		}
		xWall := make([][]int, h)
		yWall := make([][]int, h)
		for i := 0; i < h; i++ {
			xWall[i], yWall[i] = make([]int, w), make([]int, w)
			for j := 0; j < w; j++ {
				xWall[i][j], yWall[i][j] = -1, -1
			}
		}
		for i := 0; i < h*2-1; i++ {
			if i%2 == 0 {
				for j := 0; j < w-1; j++ {
					xWall[i/2][j] = io.NextInt()
				}
			} else {
				for j := 0; j < w; j++ {
					yWall[i/2][j] = io.NextInt()
				}
			}
		}
		//io.Println(bfs(w, h, xWall, yWall))
		fmt.Println(bfs(w, h, xWall, yWall))
	}
}

type P struct {
	x, y int
}

func bfs(w, h int, x, y [][]int) int {
	d := make([][]int, h)
	for i := 0; i < h; i++ {
		d[i] = make([]int, w)
	}
	q := list.New()
	q.PushBack(P{0, 0})
	d[0][0] = 1

	for q.Len() != 0 {
		pos := q.Remove(q.Front()).(P)
		if pos.x == w-1 && pos.y == h-1 {
			break
		}
		if pos.x > 0 && x[pos.y][pos.x-1] == 0 && d[pos.y][pos.x-1] == 0 {
			d[pos.y][pos.x-1] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x - 1, pos.y})
		}
		if pos.x < w-1 && x[pos.y][pos.x] == 0 && d[pos.y][pos.x+1] == 0 {
			d[pos.y][pos.x+1] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x + 1, pos.y})
		}
		if pos.y > 0 && y[pos.y-1][pos.x] == 0 && d[pos.y-1][pos.x] == 0 {
			d[pos.y-1][pos.x] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x, pos.y - 1})
		}
		if pos.y < h-1 && y[pos.y][pos.x] == 0 && d[pos.y+1][pos.x] == 0 {
			d[pos.y+1][pos.x] = d[pos.y][pos.x] + 1
			q.PushBack(P{pos.x, pos.y + 1})
		}
	}
	return d[h-1][w-1]
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := []interface{}{}
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include<iostream>
#include<queue>
#include<utility>
#include<algorithm>
#define N 40
#define INF 1000
#define Pair pair<int,int>
#define x first
#define y second

using namespace std;

int h, w;
int data[N][N];
bool H[N][N], V[N][N];
int X[]={-1, 0, 0, 1};
int Y[]={0, -1, 1, 0};

void init(){
  for(int i=0; i<N; ++i){
    for(int j=0; j<N; ++j){
      data[i][j]=INF;
      H[i][j]=true;
      V[i][j]=true;
    }
  }
}

void input(){
  for(int i=0; i<2*h-1; ++i){
    if(i%2){
      for(int j=0; j<w; ++j) cin >> H[i/2][j];
    }else{
      for(int j=0; j<w-1; ++j) cin >> V[i/2][j];
    }
  }
}

bool check(const Pair& p, int& k){
  if(!(p.x>=0 && p.x<h)) return false;
  if(!(p.y>=0 && p.y<w)) return false;
  if(data[p.x][p.y]<INF) return false;
  if(k==0) return !H[p.x][p.y];
  if(k==1) return !V[p.x][p.y];
  if(k==2) return !V[p.x][p.y-1];
  if(k==3) return !H[p.x-1][p.y];
  return false;
}

int bfs(){
  queue<Pair> qu;
  qu.push(Pair(0,0));
  data[0][0]=1;
  while(!qu.empty() && data[h-1][w-1]==INF){
    int s=qu.size();
    for(int i=0; i<s; ++i){
      Pair p1=qu.front(); qu.pop();
      for(int j=0; j<4; ++j){
	Pair p2(p1.x+X[j], p1.y+Y[j]);
	if(check(p2,j)){
	  data[p2.x][p2.y] = data[p1.x][p1.y] + 1;
	  qu.push(p2);
	}
      }
    }
  }
  return data[h-1][w-1];
}

int main(){
  while(1){
    cin >> w >> h;
    if(!w && !h) break;
    init();
    input();
    int ans=bfs();
    cout << (ans!=INF ? ans : 0) << endl;
  }
  return 0;
}

C++: #include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<queue>
#include<sstream>
using namespace std;

int w,h;
bool start(){
  string s;
  getline(cin,s);
  stringstream ss(s);
  ss>>w>>h;
  return w|h;
}
typedef pair<int,int> pii;
#define X first
#define Y second
vector<string> f;
struct S{
  int c;
  pii p;
};
bool operator<(S a,S b){
  return a.c>b.c;
}
const int vx[]= {0,0,1,-1};
const int vy[]= {1,-1,0,0};
const bool check(int x,int y){
  return (0<=x)&&(x<f.size())&&(0<=y)&&(y<f[x].size());
}
int find(pii start,pii end){
  priority_queue<S> q;
  q.push(S{1,start});
  vector<vector<int>> dp(f.size(),vector<int>(f[0].size(),-1));
  while(!q.empty()){
    S now = q.top();q.pop();
    if(now.p == end){
      return now.c;
    }
    if(dp[now.p.X][now.p.Y]!=-1)continue;
    dp[now.p.X][now.p.Y]=now.c;
    for(int i=0;i<4;i++){
      const int x = now.p.X+vx[i];
      const int y = now.p.Y+vy[i];
      if(check(x,y)&&f[x][y]!='1'){
        q.push(S{now.c+(f[x][y]=='*'),pii(x,y)});
      }
    }
  }
  return -1;
}



int solve(){
  f.clear();f.resize(2*h-1);
  for(int i=0;i<f.size();i++){
    getline(cin,f[i]);
    if(i%2==0)f[i]=f[i]+=' ';
  }
  for(int i=0;i<f.size();i+=2){
    for(int j=0;j<f[i].size();j+=2){
      f[i][j]='*';
    }
  }
  for(int i=0;i<f.size();i++){
    for(int j=0;j<f[i].size();j++){
      if(f[i][j]==' '){
        f[i][j]='1';
      }
    }
  }
  return find(pii(0,0),pii(f.size()-1,f[0].size()-1));
}

int main(){
  while(start()){
    cout<<solve()<<endl;
  }
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <set>
using namespace std;
typedef long long ll;

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

int h,w;

int d[50][50];
bool g[50][50][4];

int main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	while(1){
		cin >> w >> h;
		if(w==0&&h==0)break;
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				d[i][j]=1e9;
				for(int k=0;k<4;k++){
					g[i][j][k]=0;
				}
			}
		}
		for(int i=0;i<h-1;i++){
			for(int j=0;j<w-1;j++){
				int ww; cin >> ww;
				if(ww){
					g[i][j][2]=g[i][j+1][3]=1;
				}
			}
			for(int j=0;j<w;j++){
				int ww; cin >> ww;
				if(ww){
					g[i][j][0]=g[i+1][j][1]=1;
				}
			}
		}
		for(int j=0;j<w-1;j++){
			int ww; cin >> ww;
			if(ww){
				g[h-1][j][2]=g[h-1][j+1][3]=1;
			}
		}
		d[0][0]=0;
		queue<pair<int,int>> q; q.push(make_pair(0,0));
		while(q.size()){
			auto p=q.front(); q.pop();
			int x=p.first,y=p.second;
			for(int i=0;i<4;i++){
				if(g[x][y][i])continue;
				int nx=x+dx[i],ny=y+dy[i];
				if(0<=nx&&nx<h&&0<=ny&&ny<w){
					if(d[nx][ny]>d[x][y]+1){
						d[nx][ny]=d[x][y]+1;
						q.push(make_pair(nx,ny));
					}
				}
			}
		}
		if(d[h-1][w-1]>=1e9){
			printf("0\n");
		}else{
			printf("%d\n",d[h-1][w-1]+1);
		}
	}
}