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]
			}
			if now==next {
				continue
			}
			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<bits/stdc++.h>
#define MP make_pair
#define F first
#define S second
using namespace std;
typedef pair<int, int> PII;
typedef pair<PII, PII> PPP;

int x, y;
bool visited[51][51][51][51];
bool flr[52][52];
int dx[] = {0, 1, 0, -1}, dy[] = {1, 0, -1, 0};
int main()
{
  while(true){
    cin >> x >> y;
    if(!x && !y){
      break;
    }

    int tx, ty, kx, ky;
    memset(visited, false, sizeof visited);
    memset(flr, false, sizeof flr);
    cin >> tx >> ty >> kx >> ky;

    for(int i = 1; i <= y; i++){
      for(int j = 1; j <= x; j++){
	int in;
	cin >> in;
	flr[i][j] = (bool)in;
      }
    }

    for(int i = 1; i <= y; i++){
      flr[i][0] = flr[i][x + 1] = true;
    }
    for(int i = 1; i <= x; i++){
      flr[0][i] = flr[y + 1][i] = true;
    }

    queue<PPP> q;
    q.push(MP(MP(ty, tx), MP(ky, kx)));

    for(int i = 0; i <= 100; i++){
      int sz = q.size();
      for(int j = 0; j < sz; j++){
	PPP now = q.front();
	q.pop();
	if(!visited[now.F.F][now.F.S][now.S.F][now.S.S]){
	  visited[now.F.F][now.F.S][now.S.F][now.S.S] = true;
	  
	  if(now.F.F == now.S.F && now.F.S == now.S.S){
	    cout << i << endl;
	    goto end;
	  }
	  
	  for(int k = 0; k < 4; k++){
	    int ntdx = dx[k], ntdy = dy[k], nkdx = -dx[k], nkdy = -dy[k];
	    PPP next = MP(MP(now.F.F + ntdy * !flr[now.F.F + ntdy][now.F.S + ntdx], now.F.S + ntdx * !flr[now.F.F + ntdy][now.F.S + ntdx]), MP(now.S.F + nkdy * !flr[now.S.F + nkdy][now.S.S + nkdx], now.S.S + nkdx * !flr[now.S.F + nkdy][now.S.S + nkdx]));
	    q.push(next);
	  }
	}
      }
    }
    cout << "NA" << endl;
  end:;
  }
  return 0;
}

C++: #include <algorithm>
#include <map>
#include <vector>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cstring>
#include <cctype>
#include <cstdlib>
#include <cmath>
#include <string>
#include <queue>
#include <stack>
#include <set>
using namespace std;

#define REP(i,n) for(int i=0; i<n; ++i)
#define IREP(it,array) for(vector<int>::iterator it=array.begin(); it!=array.end(); ++it)
#define PREP(it,array) for(vector<P>::iterator it=array.begin(); it!=array.end(); ++it)
#define SREP(it,array) for(vector<string>::iterator it=array.begin(); it!=array.end(); ++it)

#define MP       make_pair
#define PB       push_back
#define ALL(x)   (x).begin(),(x).end()

const int INF = 1<<29;
const double EPS = 1e-9;
double zero(double d){
  return d < EPS ? 0.0 : d;
}

typedef long long LL;
typedef pair<int,int> P;

int dx[] = {0,1,0,-1};
int dy[] = {1,0,-1,0};

struct Sta{
  int ax,ay;
  int bx,by;
  int count;
};

int main()
{
  cout.setf(ios::fixed, ios::floatfield);
  cout.precision(7);

  int X,Y;
  while( cin>>X>>Y, X ){
    int tx,ty;
    cin >>tx>>ty;

    int kx,ky;
    cin>>kx>>ky;

    bool dep[Y+1][X+1];
    REP(i,Y){
      REP(j,X){
	int ttt;
	cin >> ttt;
	dep[i+1][j+1] = ttt;
      }
    }

    bool used[X+1][Y+1][X+1][Y+1];
    memset( used, 0, sizeof(used) );

    queue<Sta> que;
    Sta s;
    s.ax = tx;
    s.ay = ty;
    s.bx = kx;
    s.by = ky;
    s.count = 0;
    que.push(s);

    int res=101;
    while( ! que.empty() ){
      Sta t = que.front(); que.pop();
      if( t.ax == t.bx && t.ay == t.by ){
	res = min(res,t.count);
	break;
      }

      if( t.count >= 100 ){
	break;
      }
	
      REP(i,4){
	Sta t2 = t;
	t2.count++;

	int nAx = t2.ax + dx[i];
	int nAy = t2.ay + dy[i];
	int nBx = t2.bx + dx[(i+2)%4];
	int nBy = t2.by + dy[(i+2)%4];
	if( 0<nAx && nAx <= X && 0<nAy && nAy<=Y ){
	  if( ! dep[nAy][nAx] ){
	    t2.ax = nAx;
	    t2.ay = nAy;
	  }
	}
	if( 0<nBx && nBx <= X && 0<nBy && nBy<=Y ){
	  if( ! dep[nBy][nBx] ){
	    t2.bx = nBx;
	    t2.by = nBy;
	  }
	}

	if( ! used[t2.ax][t2.ay][t2.bx][t2.by] ){
	  used[t2.ax][t2.ay][t2.bx][t2.by] = true;
	  que.push(t2);
	}
      }
    }

    if(res==101)
      cout << "NA" << endl;
    else
      cout << res << endl;
  }

  return 0;
}