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 := 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++
			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<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<queue>
using namespace std;
typedef struct P{
  int tx,ty,kx,ky,c;
};
int dx[4]={0,1,0,-1};
int dy[4]={-1,0,1,0};
int d[55][55];
int used[55][55][55][55];
int X,Y;
P fa;
int main(void){
  int ans;
  while(1){
    scanf("%d %d",&X,&Y);
    if(!X && !Y) break;
    scanf("%d %d %d %d",&fa.tx,&fa.ty,&fa.kx,&fa.ky);
    fa.c=0;
    for(int i=1;i<=Y;i++){
      for(int j=1;j<=X;j++){
	scanf("%d",&d[j][i]);
      }
    }
    ans=-1;
    memset(used,0,sizeof(used));
    queue<P> que;
    que.push(fa);
    while(!que.empty()){
      P p=que.front();
      que.pop();
      used[p.tx][p.ty][p.kx][p.ky]=1;
      if(p.c>100)break;
      if(p.tx==p.kx && p.ty==p.ky){
	ans=p.c;
	break;
      }
      for(int i=0;i<4;i++){
	int f=0;
	int x[2]={p.tx,p.kx};
	int y[2]={p.ty,p.ky};
	for(int j=0;j<2;j++){
	  int t=1;
	  if(j)t=-1;
	  if(0<x[j]+dx[i]*t && x[j]+dx[i]*t<=X && 0<y[j]+dy[i]*t && y[j]+dy[i]*t<=Y){
	    if(!d[x[j]+dx[i]*t][y[j]+dy[i]*t]){
	      x[j]+=dx[i]*t;
	      y[j]+=dy[i]*t;
	      f+=1;
	    }
	  }
	}
	if(!f)continue;
	if(used[x[0]][y[0]][x[1]][y[1]])continue;
	P pu={x[0],y[0],x[1],y[1],p.c+1};
	que.push(pu);
      }
    }
    if(ans==-1)puts("NA");
    else printf("%d\n",ans);
  }
}

C++: #include<stdio.h>
#include<iostream>
#include<queue>
#include<string.h>
using namespace std;
struct Y{
int hx,hy,rx,ry,tim;
};
int mp[52][52],vh[52][52],vr[52][52];
int main(){
int n,w,h,i,j,a[2]={1,-1},b[2],g,k;
Y e;
while(1){
queue<Y> q;
	g=0;
	k=0;
	cin>>w>>h;
	if(w==0&&h==0)break;
	cin>>e.hx>>e.hy>>e.rx>>e.ry;
	e.tim=0;
	q.push(e);
	memset(mp,0,sizeof(mp));
	memset(vh,0,sizeof(vh));
	memset(vr,0,sizeof(vr));
	for(i=0;i<=h+1;i++){
		mp[i][0]=1;
		mp[i][w+1]=1;
	}
	for(i=0;i<=w+1;i++){
		mp[0][i]=1;
		mp[h+1][i]=1;
	}
	for(i=1;i<=h;i++){
		for(j=1;j<=w;j++){
			cin>>mp[j][i];
			if(mp[j][i]==1)k++;
		}
	}
	while(!q.empty()){
		e=q.front();
		q.pop();
				if(vh[e.hy][e.hx]==0&&vr[e.hy][e.hx]==0)g++;
				if(vr[e.ry][e.rx]==0&&vh[e.ry][e.rx]==0)g++;
				vh[e.hy][e.hx]=1;
				vr[e.ry][e.rx]=2;
		if(e.tim>=100||e.hx==e.rx&&e.hy==e.ry||g==w*h-k)break;
		e.tim++;
		for(i=0;i<2;i++){
			if(mp[e.hy+a[i]][e.hx]!=1&&vh[e.hy+a[i]][e.hx]!=1&&vr[e.ry-a[i]][e.rx]!=2||mp[e.ry-a[i]][e.rx]!=1&&vr[e.ry-a[i]][e.rx]!=2&&vh[e.hy+a[i]][e.hx]!=1){
				b[0]=0;
				b[1]=0;
				if(mp[e.hy+a[i]][e.hx]!=1){
					e.hy+=a[i];
					b[0]=1;
				}
				if(mp[e.ry-a[i]][e.rx]!=1){
					e.ry-=a[i];
					b[1]=1;
				}
				if(vh[e.hy][e.hx]==0&&vr[e.hy][e.hx]==0)g++;
				if(vr[e.ry][e.rx]==0&&vh[e.ry][e.rx]==0)g++;
				vh[e.hy][e.hx]=1;
				vr[e.ry][e.rx]=2;
				q.push(e);
				if(b[0]==1)e.hy-=a[i];
				if(b[1]==1)e.ry+=a[i];
			}																									
			if(mp[e.hy][e.hx+a[i]]!=1&&vh[e.hy][e.hx+a[i]]!=1&&vr[e.ry][e.rx-a[i]]!=2||mp[e.ry][e.rx-a[i]]!=1&&vr[e.ry][e.rx-a[i]]!=2&&vh[e.hy][e.hx+a[i]]!=1){
				b[0]=0;
				b[1]=0;
				if(mp[e.hy][e.hx+a[i]]!=1){
					e.hx+=a[i];
					b[0]=1;
				}
				if(mp[e.ry][e.rx-a[i]]!=1){
					e.rx-=a[i];
					b[1]=1;
				}
				if(vh[e.hy][e.hx]==0&&vr[e.hy][e.hx]==0)g++;
				if(vr[e.ry][e.rx]==0&&vh[e.ry][e.rx]==0)g++;
				vh[e.hy][e.hx]=1;
				vr[e.ry][e.rx]=2;
				q.push(e);
				if(b[0]==1)e.hx-=a[i];
				if(b[1]==1)e.rx+=a[i];
			}
		}
		e.tim--;
	}
	if(e.tim>=100||g==w*h-k||q.empty())printf("NA\n");
	else cout<<e.tim<<endl;
}
return 0;
}