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(102)
	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 == 102 {
		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<stdio.h>
#include<list>

class pos{
 public:
  int x1;
  int y1;
  int x2;
  int y2;
  pos(int xa1,int ya1,int xa2,int ya2){
    x1=xa1;
    y1=ya1;
    x2=xa2;
    y2=ya2;
  }
  bool eq(){
    return x1==x2&&y1==y2;
  }
};

char map[52][52];

int main(){
  int i,j,x,y,tx,ty,kx,ky,b,dir[][2]={{1,0},{-1,0},{0,1},{0,-1}};
  using namespace std;
  list<pos> mlst,add,now;
  list<pos>::iterator it,se;
  pos *nx;
  for(i=0;i<52;i++) map[i][0]=map[0][i]=1;
  do{
    scanf("%d %d",&x,&y);
    if(!x&&!y) break;
    mlst.clear();
    now.clear();
    scanf("%d %d",&tx,&ty);
    scanf("%d %d",&kx,&ky);
    if(tx==kx&&ky==ty){
      printf("0\n");
      goto meet;
    }
    nx=new pos(tx,ty,kx,ky);
    mlst.push_back(*nx);
    now.push_back(*nx);
    for(i=0;i<y;i++){
      for(j=0;j<x-1;j++){
	scanf("%d ",&b);
	map[i+1][j+1]=b;
      }
      scanf("%d",&b);
      map[i+1][j+1]=b;
      map[i+1][j+2]=1;
    }
    for(i=1;i<x+2;i++) map[y+1][i]=1;
    for(i=1;i<100;i++){
      it=now.begin();
      while(it!=now.end()){
	for(j=0;j<4;j++){
	  if(map[it->y1+dir[j][0]][it->x1+dir[j][1]]){
	    tx=it->x1;
	    ty=it->y1;
	  }else{
	    tx=it->x1+dir[j][1];
	    ty=it->y1+dir[j][0];
	  }
	  if(map[it->y2+-1*dir[j][0]][it->x2+-1*dir[j][1]]){
	    kx=it->x2;
	    ky=it->y2;
	  }else{
	    kx=it->x2+-1*dir[j][1];
	    ky=it->y2+-1*dir[j][0];
	  }
	  se=add.begin();
	  while(se!=add.end()){
	    if(se->x1==tx&&se->y1==ty&&
	       se->x2==kx&&se->y2==ky) goto cont;
	    se++;
	  }
	  se=mlst.begin();
	  while(se!=mlst.end()){
	    if(se->x1==tx&&se->y1==ty&&
	       se->x2==kx&&se->y2==ky) goto cont;
	    se++;
	  } 
	  nx=new pos(tx,ty,kx,ky);
	  if(nx->eq()){
	    printf("%d\n",i);
	    add.clear();
	    goto meet;
	  }
	  add.push_back(*nx);
	cont:;
	}
	it++;
      }
      if(add.empty()){
	printf("NA\n");
	goto meet;
      }
      now.clear();
      now.insert(now.end(),add.begin(),add.end());
      mlst.insert(mlst.end(),add.begin(),add.end());
      add.clear();
    }
    printf("NA\n");
  meet:;
  }while(1);
  return 0;
}

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

int w,h;
int tx,ty;
int kx,ky;
int maze[100][100]; //y,x
bool d[55][55][55][55];
int dx[] = {1,0,0,-1};
int dy[] = {0,1,-1,0};
struct P{
  int f,s,sf,ss,c;
  P (int f,int s,int sf,int ss,int c):f(f),s(s),sf(sf),ss(ss),c(c) {};
};

int bfs(){
  queue < P > que;
  que.push( P(tx,ty,kx,ky,0) );
  d[tx][ty][kx][ky] = true;

  int cnt = 0;
  while( !que.empty() ){
    P p = que.front(); que.pop();

    if(p.f == p.sf && p.s == p.ss) return p.c;
    if(cnt == 100) return -1;

    cnt++;
    for(int i=0;i<4;i++){
      int ntx = p.f + dx[i];
      int nty = p.s + dy[i];
      int nkx = p.sf + dx[3-i];
      int nky = p.ss + dy[3-i];

      if(ntx < 0 || nty < 0 || ntx == w || nty == h || maze[nty][ntx] == 1){
	ntx = p.f;
	nty = p.s;
      }

      if(nkx < 0 || nky < 0 || nkx == w || nky == h || maze[nky][nkx] == 1){
	nkx = p.sf;
	nky = p.ss;
      }

      if(!d[ntx][nty][nkx][nky]){
	d[ntx][nty][nkx][nky] = true;
	que.push( P(ntx,nty,nkx,nky,p.c+1) );
      }
    }
  }
}

int main(){

  while(true){
    cin >> w >> h;
    if(!w && !h) break;

    cin >> tx >> ty;
    cin >> kx >> ky;

    tx--; ty--; kx--; ky--;

    memset(maze,0,sizeof(maze));
    memset(d,false,sizeof(d));

    for(int i=0;i<h;i++){
      for(int j=0;j<w;j++) cin >> maze[i][j];
    }

    int ans = bfs();

    if(ans < 0) cout << "NA\n";
    else cout << ans << endl;

  }
}