Go: package main

import (
	"fmt"
	"math"
)

type Position struct {
	X int64
	Y int64
}

func (one Position) Distance(another Position) int64 {
	return int64(math.Abs(float64(one.X-another.X)) + math.Abs(float64(one.Y-another.Y)))
}

type PersonPosition struct {
	Takayuki Position
	Kazuyuki Position
}

func (one PersonPosition) Distance() int64 {
	return one.Takayuki.Distance(one.Kazuyuki)
}

type Status struct {
	Person PersonPosition
	Turn   int64
}

type PQStatus []*Status

func (pq PQStatus) Len() int {
	return len(pq)
}
func (pq PQStatus) Less(i, j int) bool {
	if pq[i].Turn == pq[j].Turn {
		return pq[i].Person.Distance() < pq[j].Person.Distance()
	}
	return pq[i].Turn < pq[j].Turn
}

func (pq PQStatus) Swap(i, j int) {
	pq[i], pq[j] = pq[j], pq[i]
}

func (pq *PQStatus) Push(x interface{}) {
	item := x.(*Status)
	*pq = append(*pq, item)
}

func (pq *PQStatus) Pop() interface{} {
	old := *pq
	n := len(old)
	item := old[n-1]
	*pq = old[0 : n-1]
	return item
}

func solve(h, w int64) {
	var tx, ty, kx, ky int64
	fmt.Scan(&tx, &ty, &kx, &ky)
	tx--
	ty--
	kx--
	ky--
	m := make([][]int64, h)
	for i := range m {
		m[i] = make([]int64, w)
		for j := int64(0); j < w; j++ {
			fmt.Scan(&m[i][j])
		}
	}
	start := &Status{Person: PersonPosition{Takayuki: Position{X: tx, Y: ty}, Kazuyuki: Position{X: kx, Y: ky}}, Turn: 0}
	pq := make(PQStatus, 0)
	//heap.Init(&pq)
	//heap.Push(&pq, start)
	//pq.Push(start)
	pq = append(pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]int64, 0)
	ans := int64(101)
	for pq.Len() > 0 {
		//now := heap.Pop(&pq).(*Status)
		//now := pq.Pop().(*Status)
		now := pq[0]
		pq = pq[1:]
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if ans <= now.Turn {
			continue
		}

		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		for i := 0; i < 4; i++ {
			next := &Status{}
			*next = *now
			next.Person.Kazuyuki.X += dx[i]
			next.Person.Kazuyuki.Y += dy[i]
			if next.Person.Kazuyuki.X < 0 || next.Person.Kazuyuki.X >= w ||
				next.Person.Kazuyuki.Y < 0 || next.Person.Kazuyuki.Y >= h ||
				m[next.Person.Kazuyuki.Y][next.Person.Kazuyuki.X] == 1 {
				next.Person.Kazuyuki.X -= dx[i]
				next.Person.Kazuyuki.Y -= dy[i]
			}
			next.Person.Takayuki.X -= dx[i]
			next.Person.Takayuki.Y -= dy[i]
			if next.Person.Takayuki.X < 0 || next.Person.Takayuki.X >= w ||
				next.Person.Takayuki.Y < 0 || next.Person.Takayuki.Y >= h ||
				m[next.Person.Takayuki.Y][next.Person.Takayuki.X] == 1 {
				next.Person.Takayuki.X += dx[i]
				next.Person.Takayuki.Y += dy[i]
			}
			next.Turn += 1
			if next.Turn < 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				pq = append(pq, next)
			}
		}
	}
	if ans == 101 {
		fmt.Println("NA")
	} else {
		fmt.Println(ans)
	}
}

func main() {
	var h, w int64
	for {
		fmt.Scan(&h, &w)
		if h == 0 && w == 0 {
			break
		}
		solve(h, w)
	}
}

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

bool d[50][50][50][50];
int X, Y, tx, ty, kx, ky;
int dx[] = {0, 0, 1, -1}, dy[] = {1, -1, 0, 0}, mem[50][50];
int main()
{
loop:
  cin >> X >> Y;
  if(!X)
    return 0;
  cin >> tx >> ty >> kx >> ky;
  tx--; ty--; kx--; ky--;
  for(int y = 0; y < Y; y++)
  {
    for(int x = 0; x < X; x++)
    {
      int a;
      cin >> a;
      mem[y][x] = a;
    }
  }

  fill_n((bool*)d, 50 * 50 * 50 * 50, false);
  
  queue<int> q;
  q.push(tx);
  q.push(ty);
  q.push(kx);
  q.push(ky);
  q.push(0);
  while(!q.empty())
  {
    int x1 = q.front(); q.pop();
    int y1 = q.front(); q.pop();
    int x2 = q.front(); q.pop();
    int y2 = q.front(); q.pop();
    int n = q.front(); q.pop();
    
    if(n > 100)
    {
      cout << "NA" << endl;
      break;
    }
    
    if(y1 == y2 && x1 == x2)
    {
      cout << n << endl;
      goto loop;
    }

    for(int i = 0; i < 4; i++)
    {
      int tx1 = x1 + dx[i];
      int ty1 = y1 + dy[i];
      int tx2 = x2 - dx[i];
      int ty2 = y2 - dy[i];

      bool b1 = ty1 < 0 || ty1 >= Y || tx1 < 0 || tx1 >= X || mem[ty1][tx1] == 1;
      bool b2 = ty2 < 0 || ty2 >= Y || tx2 < 0 || tx2 >= X || mem[ty2][tx2] == 1;

      if(b1)
      {
        tx1 = x1;
        ty1 = y1;
      }
      if(b2)
      {
        tx2 = x2;
        ty2 = y2;
      }
      if(d[tx1][ty1][tx2][ty2])
        continue; 

      d[tx1][ty1][tx2][ty2] = true;
      q.push(tx1);
      q.push(ty1);
      q.push(tx2);
      q.push(ty2);
      q.push(n + 1);
    }
  }
  cout << "NA" << endl;
  goto loop;
}

C++: #include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define INF (1 << 30)

int xs[] = {0, 1, 0, -1}, ys[] = {1, 0, -1, 0};
int x, y;
int field[50][50];
char dp[50][50][50][50];

int solve(int tx, int ty, int kx, int ky){
  int ntx, nty, nkx, nky;
  if(dp[tx][ty][kx][ky] != -1){
    return dp[tx][ty][kx][ky];
  }
  dp[tx][ty][kx][ky] = INF;
  for(int i = 0;i < 4;i++){
    ntx = tx + xs[i];
    nty = ty + ys[i];
    nkx = kx - xs[i];
    nky = ky - ys[i];
    if(ntx < 0 || ntx >= x || nty < 0 || nty >= y || field[ntx][nty] == 1){
      ntx = tx;
      nty = ty;
    }
    if(nkx < 0 || nkx >= x || nky < 0 || nky >= y || field[nkx][nky] == 1){
      nkx = kx;
      nky = ky;
    }
    dp[tx][ty][kx][ky] = min(dp[tx][ty][kx][ky], solve(ntx, nty, nkx, nky) + 1);
  }
  return dp[tx][ty][kx][ky];
}

int main(){
  int tx, ty, kx, ky;
  while(true){
    scanf("%d%d", &x, &y);
    memset(dp, -1, sizeof(dp));
    if(x == 0 && y == 0) return 0;
    scanf("%d%d", &tx, &ty);
    scanf("%d%d", &kx, &ky);
    for(int i = 0;i < y;i++){
      for(int j = 0;j < x;j++){
	scanf("%d", &field[x][y]);
	dp[i][j][i][j] = 0;
      }
    }
    int ans = solve(tx - 1, ty - 1, kx - 1, ky - 1);
    if(ans > 100)
      puts("NA");
    else
      printf("%d\n", ans);
  }
}

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

using namespace std ;

struct ST
{
	int tx ,ty ;
	int kx ,ky ;
	int cnt ;
	ST( int a ,int s ,int d ,int f ,int g ) : tx( a ) ,ty( s ) ,kx( d ) ,ky( f ) ,cnt( g ){}
} ;

int mx[ 4 ] = { 1 ,0 ,0 ,-1 } ;
int my[ 4 ] = { 0 ,1 ,-1 ,0 } ;
int map[ 50 ][ 50 ] ;

int w ,h ;
int tx ,kx ;
int ty ,ky ;

void ans()
{
	queue< ST > que ;
	bool came[ 50 ][ 50 ][ 50 ][ 50 ] = { false } ;
	que.push( ST( tx - 1 ,ty - 1 ,kx - 1 ,ky - 1 ,0 ) ) ;
	while( ! que.empty() )
	{
		ST st = que.front() ;
		if( st.tx == st.kx && st.ty == st.ky )
		{
			cout << st.cnt << endl ;
			return ;
		}
		else if( st.cnt >= 100 )
		{
			break ;
		}
		que.pop() ;
		came[ st.tx ][ st.ty ][ st.kx ][st.ky ] = true ;
		for( int i = 0 ; i < 4 ; i++ )
		{
			int j = 3 - i ;
			tx = st.tx + mx[ i ] ;
			kx = st.kx + mx[ j ] ;
			ty = st.ty + my[ i ] ;
			ky = st.ky + my[ j ] ;
			if( tx < 0 || tx >= w || ty < 0 || ty >= h || 1 * map[ ty ][ tx ] )
			{
				tx = st.tx ;
				ty = st.ty ;
			}
			if( kx < 0 || kx >= w || ky < 0 || ky >= h || 1 * map[ ky ][ kx ] )
			{
				kx = st.kx ;
				ky = st.ky ;
			}
			if( came[ tx ][ ty ][ kx ][ ky ] - 1 )
			{
				que.push( ST( tx ,ty ,kx ,ky ,st.cnt + 1 ) ) ;
			}
		}
	}
	cout << "NA" << endl ;
}

int main()
{
	while( cin >> w >> h ,h )
	{
		cin >> tx >> ty ;
		cin >> kx >> ky ;
		for( int i = 0 ; i < h ; i++ )
		{
			for( int j = 0 ; j < w ; j++ )
			{
				cin >> map[ i ][ j ] ;
			}
		}
		ans() ;
	}
}