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 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)
	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 len(pq) > 0 {
		now := &Status{}
		now = pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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++
			if next.Turn <= 100 {
				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 <iostream>
#include <queue>
using namespace std;

const int INF = 1000000;
int H,W;
class Point{
public:
  int tx;
  int ty;
  int kx;
  int ky;
  void set(int a,int b,int c,int d){
    tx = a;
    ty = b;
    kx = c;
    ky = d;
  }
};

int is_out_of_area(int y,int x){
  return x < 1 || x > W || y < 1 || H > H;
}
int main(){
  char F[52][52];
  int D[52][52];

  int tx,ty,kx,ky;
  while(1){
  cin >> W >> H;
  if(W == 0 && H == 0)
    break;
  cin >> tx >> ty >> kx >> ky;

  for(int y=0;y<=H+1;y++){
    for(int x=0;x<=W+1;x++){
      F[y][x] = 1;
    }
  }
  for(int y=1;y<=H;y++){
    for(int x=1;x<=W;x++){
      D[y][x] = INF;
      int a;
      cin >> a;
      F[y][x] = a;
    }
  }

  queue<Point> qa;
  Point p;
  p.set(tx,ty,kx,ky);
  qa.push(p);
  D[p.ty][p.tx] = 0;
  while(!qa.empty()){
    p = qa.front();
    qa.pop();
    if(D[p.ty][p.tx] >= 100){
      cout << "NA" << endl;
      break;
    }
    if(p.tx == p.kx && p.ty == p.ky){
      cout << D[p.ty][p.tx] << endl;
      return 0;
    }

    if(D[p.ty-1][p.tx] == INF && D[p.ky+1][p.kx] == INF){
      if(is_out_of_area(p.ty-1,p.tx) == 0 || is_out_of_area(p.ky+1,p.kx) == 0){
        if(F[p.ty-1][p.tx] == 0 || F[p.ky+1][p.kx] == 0){
          Point q;
          q.set(p.tx,p.ty-1,p.kx,p.ky+1);
          qa.push(q);
          D[q.ty][q.tx] = D[p.ty][p.tx] + 1;
        }
      }
    }
    if(D[p.ty+1][p.tx] == INF && D[p.ky-1][p.kx] == INF){
      if(is_out_of_area(p.ty-1,p.tx) == 0 || is_out_of_area(p.ky+1,p.kx) == 0){
        if(F[p.ty+1][p.tx] == 0 || F[p.ky-1][p.kx] == 0){
          Point q;
          q.set(p.tx,p.ty+1,p.kx,p.ky-1);
          qa.push(q);
          D[q.ty][q.tx] = D[p.ty][p.tx] + 1;
        }
      }
    }
    if(D[p.ty][p.tx-1] == INF && D[p.ky][p.kx+1] == INF){
      if(is_out_of_area(p.ty,p.tx) == 0 || is_out_of_area(p.ky,p.kx) == 0){
        if(F[p.ty][p.tx-1] == 0 || F[p.ky][p.kx+1] == 0){
          Point q;
          q.set(p.tx-1,p.ty,p.kx+1,p.ky);
          qa.push(q);
          D[q.ty][q.tx] = D[p.ty][p.tx] + 1;
        }
      }
    }
    if(D[p.ty][p.tx+1] == INF && D[p.ky][p.kx-1] == INF){
      if(is_out_of_area(p.ty,p.tx+1) == 0 || is_out_of_area(p.ky,p.kx-1) == 0){
        if(F[p.ty][p.tx+1] == 0 || F[p.ky][p.kx-1] == 0){
          Point q;
          q.set(p.tx+1,p.ty,p.kx-1,p.ky);
          qa.push(q);
          D[q.ty][q.tx] = D[p.ty][p.tx] + 1;
        }
      }
    }

  }
  cout << "NA" << endl;
}
  return 0;
}

C++: #include <cstdio>
#include <queue>
#include <map>
#include <algorithm>
#define Z(n)get<n>(z)
#define M make_pair
#define F first
#define S second
using namespace std;
typedef pair<int,int> pii;
typedef tuple<pii,pii,int> T;
int t[51][51],dx[]={-1,0,1,0},dy[]={0,-1,0,1},a,b,x,y,X,Y,i,j;
int main(){
	for(;scanf("%d%d",&a,&b),a;){
		map<pair<pii,pii>,int>m;
		scanf("%d%d%d%d",&x,&y,&X,&Y);x--,y--,X--,Y--;
		for(j=0;j<b;j++)for(i=0;i<a;i++)scanf("%d",t[i]+j);
		queue<T>q;
		m[M(M(x,y),M(X,Y))]=1;
		for(q.push(make_tuple(M(x,y),M(X,Y),0));!q.empty();){
			T z=q.front();q.pop();
			if(Z(0)==Z(1)){printf("%d\n",get<2>(z));goto OK;}
			if(Z(2)<100)for(i=0;i<4;i++){
				pii c1=make_pair(Z(0).F+dx[i],Z(0).S+dy[i]);
				if(!(0<=c1.F&&c1.F<a&&0<=c1.S&&c1.S<b&&!t[c1.F][c1.S]))c1=Z(0);
				pii c2=make_pair(Z(1).F+dx[(i+2)%4],Z(1).S+dy[(i+2)%4]);
				if(!(0<=c2.F&&c2.F<a&&0<=c2.S&&c2.S<b&&!t[c2.F][c2.S]))c2=Z(1);
				if((c1!=Z(0)||c2!=Z(1))&&!m[M(c1,c2)]){
					q.push(make_tuple(c1,c2,Z(2)+1));
					m[M(c1,c2)]=1;
				}
			}
		}
		puts("NA");
		OK:;
	}
}

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

using namespace std;
class State
{
public:
  int x1,y1,x2,y2,cost;

  State(int tx1,int ty1,int tx2,int ty2,int tcost)
  {
    x1 = tx1;
    y1 = ty1;
    x2 = tx2;
    y2 = ty2;
    cost = tcost;
  }
};

int w,h;
bool t[52][52];
bool used[52][52][52][52];

int dx1[] = {-1,1,0,0};
int dx2[] = {1,-1,0,0};
int dy1[] = {0,0,1,-1};
int dy2[] = {0,0,-1,1};


void solve()
{
	while(cin>>w>>h && (w||h))
	{
    int x1,y1,x2,y2;
    cin>>x1>>y1>>x2>>y2;
    x1--; y1--; x2--; y2--;

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

    int ans = -1;
    queue<State> open;

    memset(used,0,sizeof(used));
    used[x1][y1][x2][y2] = true;
    open.push(State(x1,y1,x2,y2,0));

    while(!open.empty())
	{
      State st = open.front(); open.pop();
      if(st.cost >= 100) break;

      if(st.x1 == st.x2 && st.y1 == st.y2)
	  {
        ans = st.cost;
        break;
      }

      for(int i=0;i<4;i++)
	  {
        int nx1 = st.x1 + dx1[i];
        int ny1 = st.y1 + dy1[i];
        int nx2 = st.x2 + dx2[i];
        int ny2 = st.y2 + dy2[i];
        State nst = st;
        nst.cost++;

        if(nx1>=0 && nx1<w && ny1>=0 && ny1<h && !t[ny1][nx1])
		{
          nst.x1 = nx1;
          nst.y1 = ny1;
        }
        if(nx2>=0 && nx2<w && ny2>=0 && ny2<h && !t[ny2][nx2])
		{
          nst.x2 = nx2;
          nst.y2 = ny2;
        }

        if(!used[nst.x1][nst.y1][nst.x2][nst.y2])
		{
          used[nst.x1][nst.y1][nst.x2][nst.y2] = true;
          open.push(nst);
        }
      }
    }

    if(ans == -1)
      cout<<"NA\n";
    else
      cout<<ans<<endl;
  }

}

int main()
{
	solve();
	return(0);
}