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 <cstdio>
#include <cstdlib>
#include <math.h>
#include <vector>
#include <queue>
#include <algorithm>
#include <sstream>
#include <string>
using namespace std;
#define FOR(I,N) for(int I = 0; I < (int)(N); I++)
#define FIN(V) cout<<V<<endl
#define pb push_back
#define INF (1 << 30)
typedef pair<int, int> P;

int solve();
int dx[4] = {1, -1, 0, 0};
int dy[4] = {0, 0, 1, -1};
int w, h, tx, ty, kx, ky;
int maps[51][51];
int memo[51][51][51][51];


struct Data{
    P pt, pk;
    int cnt;
    Data(P pt_, P pk_, int cnt_){
        pt = pt_;
        pk = pk_;
        cnt = cnt_;
    }
    Data(){}
};

int main(void){
    while(cin >> w >> h, w){
        cin >> tx >> ty;
        cin >> kx >> ky;
        fill_n(*maps, 51*51, 1);
        FOR(i, h)FOR(j, w){
            cin >> maps[i+1][j+1];
        }
        int a = solve();
        if(a == -1 || a >= 100){FIN("NO");continue;}
        FIN(a);
    }
    return 0;    
}


int solve(){
    int ans = -1;
    fill_n(***memo, 51*51*51*51, INF);
    queue<Data> que;
    que.push(Data(P(tx,ty), P(kx, ky), 0));
    while(que.size()){
        Data data = que.front();
        que.pop();
        int x1 = data.pt.first;
        int y1 = data.pt.second;
        int x2 = data.pk.first;
        int y2 = data.pk.second;
        if(data.cnt > 100)break;
        if(memo[x1][y1][x2][y2] <= data.cnt)continue;
        memo[x1][y1][x2][y2] = data.cnt;
        if(x1 == x2 && y1 == y2){ans = data.cnt;break;};
        FOR(i, 4){
            int nx1 = x1 + dx[i];
            int ny1 = y1 + dy[i];
            int nx2 = x2 - dx[i];
            int ny2 = y2 - dy[i];
            if(maps[ny1][nx1] == 1){nx1 = x1;ny1 = y1;};
            if(maps[ny2][nx2] == 1){nx2 = x2;ny2 = y2;};
            que.push(Data(P(nx1,ny1), P(nx2, ny2), data.cnt++));
        }
    }

    return ans;
}

C++: #include<iostream>
#include<queue>
using namespace std;
struct xy{
  int tx,ty;
  int kx,ky;
  int ti;
};
int x,y;
xy tk;
int m[51][51],v[51][51][51][51]={};
int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};

void set(){
    for(int i=1;i<=x;i++)
      for(int j=1;j<=y;j++)
	for(int k=1;k<=x;k++)
	  for(int l=1;l<=y;l++)v[i][j][i][j]=0;
    

}

bool g(int a,int b){
  if(a<1 || a>x || b<1 || b>y) return 0;
  return 1;
}

int bfs(){
  queue<xy> q;
  xy t,tmp;
  int ta,tb,ka,kb,ans=10000,tim,cnt=0;
  q.push(tk);
  while(!q.empty()){
    t=q.front(),q.pop();
        for(int i=0;i<4;i++){
      ta=t.tx+dx[i],tb=t.ty+dy[i],ka=t.kx-dx[i],kb=t.ky-dy[i],tim=t.ti+1;
      if(g(ta,tb) || g(ka,kb)){
	if(!g(ta,tb))ta=t.tx,tb=t.ty;
	if(!g(ka,kb)) ka=t.kx,kb=t.ky;
	if(v[ta][tb][ka][kb]==1)continue;
	if(m[ta][tb]==1 && m[ka][kb]==1) continue;
	if(m[ta][tb]==1) tmp.tx=t.tx,tmp.ty=t.ty;
	else tmp.tx=ta,tmp.ty=tb;
	if(m[ka][kb]==1) tmp.kx=t.kx,tmp.ky=t.ky;
	else tmp.kx=ka,tmp.ky=kb;
	v[ta][tb][ka][kb]=1;
	tmp.ti=tim;
	cnt++;
       	if(tmp.ti>=100)  break;
	if(tmp.tx==tmp.kx && tmp.ky==tmp.ty){
	  if(ans>tmp.ti) ans=tmp.ti;
	  continue;
	}
	q.push(tmp);
      }
    }
  }
  return ans;
}

int main(){
  while(1){
    int ans;
    cin>>x>>y;
    if(x+y==0) break;
    cin>>tk.tx>>tk.ty>>tk.kx>>tk.ky;
    for(int i=1;i<=x;i++)
      for(int j=1;j<=y;j++)
	for(int k=1;k<=x;k++)
	  for(int l=1;l<=y;l++)v[i][j][k][l]=0;
      v[tk.tx][tk.ty][tk.kx][tk.ky]=1;
    tk.ti=0;
    for(int i=1;i<=x;i++)
      for(int j=1;j<=y;j++) cin>>m[i][j];
    ans=bfs();
    if(ans<100) cout<<ans<<endl;
    else cout<<"NA"<<endl;

  }
  
  return 0;
}