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<limits.h>
using namespace std;
int dy[] = { 0, 1, 0, -1 };
int dx[] = { 1, 0, -1, 0 };
static int map[1000][1000];
static int minPath[1000][1000];
typedef struct d Data;
struct d
{
	int x;
	int y;
	int count;
};
int main()
{
	int w, h;
	while (cin >> w >> h && w != 0 || h != 0)
	{
		for (int i = 0; i < 1000; i++)
		{
			for (int j = 0; j < 1000; j++)
			{
				map[i][j] = 0;
			}
		}

		for (int i = 0; i < h + (h - 1); i++)
		{
			for (int j = (i + 1) % 2; j < w + (w - 1); j+=2)
			{
				cin >> map[i][j];
			}
		}
		for (int i = 0; i < h + (h - 1); i++)
		{
			for (int j = 0; j < w + (w - 1); j++)
			{
				minPath[i][j] = INT_MAX;
			}
		}

		int ans = 0;
		queue<Data> q;
		Data first;
		first.x = 0;
		first.y = 0;
		first.count = 1;
		q.push(first);
		minPath[0][0] = 1;
		while (q.size() > 0)
		{
			Data data = q.front(); q.pop();
			if (data.x == w + (w - 1) - 1 && data.y == h + (h - 1) - 1)
			{
				ans = data.count;
				break;
			}

			for (int i = 0; i < 4; i++)
			{
				int nx = data.x + dx[i] * 2;
				int ny = data.y + dy[i] * 2;
				if (nx < 0 || nx >= w + (w - 1) || ny < 0 || ny >= h + (h - 1))continue;
				int px = data.x + dx[i];
				int py = data.y + dy[i];
				if (map[py][px] == 1)continue;
				if (data.count + 1 >=minPath[ny][nx])continue;
				Data d;
				d.x = nx;
				d.y = ny;
				d.count = data.count + 1;
				minPath[ny][nx] = d.count;
				q.push(d);
			}
		}
		cout << ans << endl;

	}
	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <cctype>
#include <cstdio>
#include <math.h>
#include <map>
#include <queue>
#include <string>
using namespace std;

int w,h,V[20][21],H[21][20],field[20][21];
int sx,sy,gx,gy,d[20][20],dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};
const int INF=9999999;
typedef pair<int,int> P;

int bfs(){
    queue<P> que;
    for(int i=0;i<h;i++){
	for(int j=0;j<w;j++)d[i][j]=INF;
    }
    que.push(P(sy,sx));
    d[sx][sy]=0;
    while(que.size()){
	P p=que.front(); que.pop();
	if(p.first==gx&&p.second==gy)break;
	for(int i=0;i<4;i++){
	    int nx=p.first+dx[i],ny=p.second+dy[i];
	    if(0<=nx&&nx<h&&0<=ny&&ny<w&&d[nx][ny]==INF&&(i==0&&H[nx][ny+1]==0||i==1&&V[nx+1][ny]==0||i==2&&H[nx+1][ny+1]==0||i==3&&V[nx+1][ny+1]==0)){
		que.push(P(nx,ny));
		d[nx][ny]=d[p.first][p.second]+1;
	    }
	}
    }
    return d[gx][gy];
}

int main() {
    while(cin>>w>>h){
    	if(w+h==0)return 0;
    	for(int i=0;i<h;i++){
    		for(int j=0;j<w-1;j++)cin>>V[i+1][j+1];
    		if(i!=h-1)for(int j=0;j<w;j++)cin>>H[i+1][j+1];
    	}
    	sx=0;sy=0;gx=h-1;gy=w-1;
    	if(bfs()==INF)cout<<0<<endl;
    	else cout<<bfs()+1<<endl;
    }
}

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

void solve(int w, int h, int W, int H,
const vector<string>& mmap,
vector<vector<int>>& min_lens,
int len, int& ret) {
    if (min_lens[h][w] <= len) return;
    min_lens[h][w] = len;
    if (w == W-1 && h == H-1 && (ret == 0 || ret > len)) {
        ret = len;
        return;
    }
    const vector<int> dw = {1, 0, -1, 0}, dh = {0, 1, 0, -1};
    for (int i = 0; i < 4; ++i) {
        int nw = w + dw[i], nh = h + dh[i];
        if (0 <= nw && nw < W && 0 <= nh && nh < H &&
            mmap[2*h + dh[i]][2*w + dw[i]] == '0') {
            solve(nw, nh, W, H, mmap, min_lens, len+1, ret);
        }
    }
}

int main() {
    while (true) {
        int h, w; cin >> w >> h;
        if (h == 0 && w == 0) break;
        string dammy;
        getline(cin, dammy);
        vector<string> mmap;
        for (int i = 0; i < 2*h-1; i++) {
            string e; getline(cin, e);
            if (i % 2 == 0) e.push_back(' ');
            mmap.push_back(e);
        }
        vector<vector<int>> min_lens;
        for (int i = 0; i < h; i++) {
            min_lens.emplace_back(w, h*w + 1);
        }
        int ret = 0;
        solve(0, 0, w, h, mmap, min_lens, 1, ret);
        cout << ret << endl;
    }
    return 0;
}