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)
	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)
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		if v, ok := memo[now.Person]; ok && v <= now.Turn {
			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)
			}
		}
	}
	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<queue>
using namespace std;

const int INF =100000000;

class Point{
public:
  int tx;
  int ty;
  int kx;
  int ky;
};

int main(){
  int N,M;
  while(cin>>N>>M,N || M){
      int o_tx,o_ty;
      int o_kx,o_ky;
      cin>>o_tx>>o_ty;
      cin>>o_kx>>o_ky;
      int F[52][52];
      for(int y=0;y<=N+1;y++){
        for(int x=0;x<=M+1;x++){
          F[y][x]=1;
        }
      }

      for(int y=1;y<=N;y++){
        for(int x=1;x<=M;x++){
          cin>>F[y][x];
        }
      }

      int D[52][52];
      for(int y=1;y<=N;y++){
        for(int x=1;x<=M;x++){
          D[y][x]=INF;
        }
      }
      bool same_pos[52][52][52][52];
      for(int i=1;i<=N;i++){
        for(int j=1;j<=M;j++){
          for(int k=1;k<=N;k++){
            for(int q=1;q<=M;q++){
              same_pos[i][j][k][q]=false;
            }
          }
        }
      }
      queue<Point> que;
      Point p;
      p.tx=o_tx;p.ty=o_ty;
      p.kx=o_kx;p.ky=o_ky;
      que.push(p);
      D[p.ty][p.tx]=0;

      while(!que.empty()){
        p=que.front();que.pop();
        if(same_pos[p.ty][p.tx][p.ky][p.kx])continue;
        same_pos[p.ty][p.tx][p.ky][p.kx]=true;
        if(D[p.ty][p.tx]==100)break;
        if(p.tx==p.kx&&p.ty==p.ky){
          cout<<D[p.ty][p.tx]<<endl;
          break;
        }
        if(F[p.ty-1][p.tx]!=1 || F[p.ky+1][p.kx]!=1){
          Point q;
          if(F[p.ty-1][p.ty]!=1){
            q.tx=p.tx;q.ty=p.ty-1;
          }
          if(F[p.ky+1][p.kx]!=1){
            q.kx=p.kx;q.ky=p.ky+1;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;

        }
        if(F[p.ty+1][p.tx]!=1 || F[p.ky-1][p.kx]!=1){
          Point q;
          if(F[p.ty+1][p.tx]!=1){
            q.tx=p.tx;q.ty=p.ty+1;
          }
          if(F[p.ky-1][p.kx]!=1){
            q.kx=p.kx;q.ky=p.ky-1;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;
        }
        if(F[p.ty][p.tx-1]!=1 || F[p.ky][p.kx+1]!=1){
          Point q;
          if(F[p.ty][p.tx-1]!=1){
            q.tx=p.tx-1;q.ty=p.ty;
          }
          if(F[p.ky][p.kx+1]!=1){
            q.kx=p.kx+1;q.ky=p.ky;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;
        }
        if(F[p.ty][p.tx+1]!=1 || F[p.ky][p.kx-1]!=1){
          Point q;
          if(F[p.ty][p.tx+1]!=1){
            q.tx=p.tx+1;q.ty=p.ty;
          }
          if(F[p.ky][p.kx-1]!=1){
            q.kx=p.kx-1;q.ky=p.ky;
          }
          que.push(q);
          D[q.ty][q.tx]=D[p.ty][p.tx]+1;
        }
      }
      if(p.tx!=p.kx || p.ty!=p.ky){
        cout<<"NA"<<endl;
      }
    }
  return 0;
}

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

#define REP(i,k,n) for(int i=k;i<n;i++)
#define rep(i,n) for(int i=0;i<n;i++)
#define INF 1<<30

using namespace std;

int dx[4] = {1,0,-1,0};
int dy[4] = {0,1,0,-1};

struct Data
{
	int tx,ty,kx,ky,cost;

	Data(int tx,int ty,int kx,int ky,int cost) : tx(tx),ty(ty),kx(kx),ky(ky),cost(cost) {}
};

int main()
{
	int x,y;
	while(cin >> x >> y)
	{
		if(x == 0 && y == 0) break;

		int tx,ty,kx,ky;
		cin >> tx >> ty >> kx >> ky;

		tx--;
		ty--;
		kx--;
		ky--;

		int field[55][55];
		memset(field,0,sizeof(field));

		rep(i,y) rep(j,x) cin >> field[i][j];

	   	bool used[52][52][52][52];
		rep(i,52) rep(j,52) rep(k,52) rep(l,52) used[i][j][k][l] = false;
		used[tx][ty][kx][ky] = true;

		queue<Data> que;
		que.push(Data(tx,ty,kx,ky,0));
		
		bool flag = false;
		int ans;

		while(que.size())
		{
			Data data = que.front();
			que.pop();

			if(data.cost >= 100) break;

			if(data.tx == data.kx && data.ty == data.ky)
			{
				flag = true;
				ans = data.cost;
				break;
			}

			rep(i,4)
			{
				int ntx = data.tx + dx[i];
				int nty = data.ty + dy[i];
				int nkx = data.kx + dx[(i+2)%4];
				int nky = data.ky + dy[(i+2)%4];

				Data nd(data.tx,data.ty,data.kx,data.ky,data.cost+1);

				if(0 <= ntx && ntx < x && 0 <= nty && nty < y && field[ntx][nty] == 0)
				{
					nd.tx = ntx;
					nd.ty = nty;
				}

				if(0 <= nkx && nkx < x && 0 <= nky && nky < y && field[nkx][nty] == 0)
				{
					nd.kx = nkx;
					nd.ky = nky;
				}

				if(!used[nd.tx][nd.ty][nd.kx][nd.ky])
				{
					used[nd.tx][nd.ty][nd.kx][nd.ky] = true;
					que.push(nd);
				}
			}

		}

		if(flag) cout << ans << endl;
		else cout << "NA" << endl;
	}
}