Go: package main

import (
	"container/heap"
	"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)
	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)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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)
			}
		}
	}
	fmt.Println("NA")
}

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>
#include<map>
#include<cstring>
using namespace std;

struct node 
{
  int step;
  int tx,ty;
  int kx,ky;
  node(int s,int ttx,int tty,int kkx,int kky):
    step(s),tx(ttx),ty(tty),kx(kkx),ky(kky){} 
};
  
int main()
{
  int x,y;
  for(;cin>>x>>y,x;)
    {
      bool data[52][52];
      int tx,ty,kx,ky;
      cin>>tx>>ty>>kx>>ky;
      memset(data,false,sizeof(data));
      for(int i=1;i<=x;i++)
	for(int j=1;j<=y;j++)
	  {
	    char tmp;
	    cin>>tmp;
	    data[j][i]=(tmp=='0');
	  }
      queue<node> qu;
      qu.push(node(0,tx,ty,kx,ky));
      map< pair<pair<int,int>,pair<int,int> > ,bool >hash;      
      int ans=-1;
      int dx[]={0,0,1,-1};
      int dy[]={1,-1,0,0};
      while(!qu.empty())
	{
	  node tmp=qu.front();
	  qu.pop();
	  //	  cout<<tmp.step<<" "<<tmp.tx<<" "<<tmp.ty<<" "<<tmp.kx<<" "<<tmp.ky<<endl;
	  if(hash[make_pair(make_pair(tmp.tx,tmp.ty),make_pair(tmp.kx,tmp.ky))])
	    continue;
	  if(tmp.tx==tmp.kx &&tmp.ty==tmp.ky)
	    {
	      ans=tmp.step;
	      break;
	    }
	  if(tmp.step>=99)
	    continue;
	  hash[make_pair(make_pair(tmp.tx,tmp.ty),make_pair(tmp.kx,tmp.ky))]=true;
	  for(int i=0;i<4;i++)
	    {
	      int ttx=tmp.tx,tty=tmp.ty,tkx=tmp.kx,tky=tmp.ky;
	      if(data[ttx+dx[i]][tty+dy[i]])
		{
		  ttx+=dx[i];
		  tty+=dy[i];
		}
	      if(data[tkx-dx[i]][tky-dy[i]])
		{
		  tkx-=dx[i];
		  tky-=dy[i];
		}
	      //cout<<"make"<<ttx<<" "<<tkx<<" "<<tty<<" "<<tty<<endl;	      
	      if(!hash[make_pair(make_pair(ttx,tty),make_pair(tkx,tky))])
		qu.push(node(tmp.step+1,ttx,tty,tkx,tky));
	    }
	}
      if(ans==-1)
	cout<<"NA"<<endl;
      else
	cout<<ans<<endl;

    }
}

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

int INF=-10;

class point{
    public:
        int x,y;
};

int main(){
    while(1){
        int w,h;
        cin>>w>>h;
        if(w+h==0){
            break;
        }
        int tx,ty;
        int kx,ky;
        cin>>tx>>ty;
        cin>>kx>>ky;

        int d[60][60];
        for(int i=0;i<60;i++){
            for(int j=0;j<60;j++){
                d[i][j]=-1;
            }
        }
        for(int i=1;i<w+1;i++){
            for(int j=1;j<h+1;j++){
                cin>>d[i][j];
                if(d[i][j]==1){
                    d[i][j]=-1;
                }
                if(d[i][j]==0){
                    d[i][j]=INF;
                }
            }
        }

        queue<point> quet;
        queue<point> quek;

        point t;
        t.x=tx; t.y=ty;
        point k;
        k.x=kx; k.y=ky;

        quet.push(t);
        quek.push(k);
        d[t.x][t.y]=0;
        d[k.x][k.y]=0;

        while(!quet.empty()||!quek.empty()){
            t=quet.front(); quet.pop();
            k=quek.front(); quek.pop();

            if(t.x==k.x&&t.y==k.y){
                break;
            }

            if(d[t.x-1][t.y]==INF&&d[k.x+1][k.y]==INF&&d[t.x-1][t.y]!=-1&&d[k.x+1][k.y]!=-1){
                point t2;
                point k2;
                t2.x=t.x-1; t2.y=t.y;
                k2.x=k.x+1; k2.y=k.y;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
            if(d[t.x+1][t.y]==INF&&d[k.x-1][k.y]==INF&&d[t.x+1][t.y]!=-1&&d[k.x-1][k.y]!=-1){
                point t2;
                point k2;
                t2.x=t.x+1; t2.y=t.y;
                k2.x=k.x-1; k2.y=k.y;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
            if(d[t.x][t.y-1]==INF&&d[k.x][k.y+1]==INF&&d[t.x][t.y-1]!=-1&&d[k.x][k.y+1]!=-1){
                point t2;
                point k2;
                t2.x=t.x; t2.y=t.y-1;
                k2.x=k.x; k2.y=k.y+1;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
            if(d[t.x][t.y+1]==INF&&d[k.x][k.y-1]==INF&&d[t.x][t.y+1]!=-1&&d[k.x][k.y-1]!=-1){
                point t2;
                point k2;
                t2.x=t.x; t2.y=t.y+1;
                k2.x=k.x; k2.y=k.y-1;
                quet.push(t2);
                quek.push(k2);
                d[t2.x][t2.y]=d[t.x][t.y]+1;
                d[k2.x][k2.y]=d[k.x][k.y]+1;
            }
        }

        if(t.x==k.x&&t.y==k.y){
            cout<<d[t.x][t.y]<<endl;
        }else{
            cout<<"NA"<<endl;
        }
    }

    return 0;
}