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 := &Status{}
		now = pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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<iostream>
#include<queue>
using namespace std;
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
int main() {
	int W, H, tx, ty, kx, ky;
	int d[52][52];
	bool memo[52][52][52][52];
	while (true) {
		cin >> W >> H;
		if (W == 0)break;
		for (int i = 0; i < W+2; i++) {
			for (int j = 0; j < H+2; j++) {
				for (int k = 0; k < W+2; k++) {
					for (int l = 0; l < H+2; l++) {
						memo[i][j][k][l] = false;
					}
				}
			}
		}
		for (int i = 0; i < W+2; i++) {
			for (int j = 0; j < H+2; j++) {
				d[i][j] = 1;
			}
		}
		cin >> tx >> ty >> kx >> ky;
		for (int i = 1; i < H + 1; i++) {
			for (int j = 1; j < W + 1; j++) {
				cin >> d[i][j];
			}
		}
		pair<pair<int, int>, pair<int, int> >num;
		num.first.first = tx;
		num.first.second = ty;
		num.second.first = kx;
		num.second.second = ky;
		queue<pair<pair<int, int>, pair<int, int> > > q;
		q.push(num);
		int qsize = 1;
		int loopcount = 0;
		while (!q.empty()) {
			num = q.front();
			q.pop();
			if (memo[num.first.first][num.first.second][num.second.first][num.second.second]) {
				continue;
			}
			else {
				memo[num.first.first][num.first.second][num.second.first][num.second.second] = true;
			}
			if (d[num.first.first][num.first.second]
				|| d[num.second.first][num.second.second]) {
				continue;
			}
			if (qsize == 0) {
				qsize = q.size();
				loopcount++;
				if (loopcount == 100) {
					cout << "NA" << endl;
					break;
				}
			}
			qsize--;
			if (num.first.first == num.second.first
				&& num.first.second == num.second.second) {
				cout << loopcount << endl;
				break;
			}
			for (int i = 0; i < 4; i++) {
				pair<pair<int, int>, pair<int, int> >copy;
				copy = num;
				copy.first.first += dx[i];
				copy.first.second += dy[i];
				copy.second.first -=dx[i];
				copy.second.second -= dy[i];
				q.push(copy);
			}
		}
	}
	return 0;
}

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

using namespace std;

struct State{
  int tx, ty, kx, ky;
  State(int tx, int ty, int kx, int ky) : tx(tx), ty(ty), kx(kx), ky(ky) {} 
};

#define MAX 51
#define INF 1e9

int H, W, tx, ty, kx, ky;
int field[MAX][MAX];
const int ttx[] = {-1,0,0,1};
const int tty[] = {0,-1,1,0};
const int kkx[] = {1,0,0,-1};
const int kky[] = {0,1,-1,0};

bool inField(int y, int x){
  return 0 <= y && y < H && 0 <= x && x < W;
}

int bfs(){
  bool vis[MAX][MAX][MAX][MAX];
  memset(vis, false, sizeof(vis));
  vis[ty][tx][ky][kx] = true;
  queue<State> Q;
  Q.push(State(tx,ty,kx,ky));
  queue<int> cnt;
  cnt.push(0);

  int res = INF;
  while(!Q.empty()){
    State s = Q.front(); Q.pop();
    int _cnt = cnt.front(); cnt.pop();

    if(_cnt == 100) break;
    if(s.tx == s.kx && s.ty == s.ky){
      res = min(res, _cnt);
      break;
    }

    for(int i = 0 ; i < 4 ; i++){
      int ntx = s.tx + ttx[i], nty = s.ty + tty[i];
      int nkx = s.kx + kkx[i], nky = s.ky + kky[i];

      if(!inField(nty, ntx) || field[nty][ntx] == 1){
        ntx = s.tx, nty = s.ty;
      }
      if(!inField(nky, nkx) || field[nky][nkx] == 1){
        nkx = s.kx, nky = s.ky;
      }

      if(vis[nty][ntx][nky][nkx]) continue;
      vis[nty][ntx][nky][nkx] = true;
      Q.push(State(ntx, nty, nkx, nky));
      cnt.push(_cnt+1);
    }
  }
  return res;
}

int main(){
  while(cin >> W >> H, (W | H)){
    cin >> tx >> ty >> kx >> ky;
    tx--, ty--, kx--, ky--;
    for(int i = 0 ; i < H ; i++){
      for(int j = 0 ; j < W ; j++){
        cin >> field[i][j];
      }
    }
    int res = bfs();
    if(res == INF){
      cout << "NA" << endl;
    }else{
      cout << res << endl;
    }
  }

  return 0;
}

C++: #include<bits/stdc++.h>
using namespace std;
int main(){
  int W,H;
  int counter=0;
  int vxt[4]={1,0,-1,0};
  int vyt[4]={0,-1,0,1};
  int vxk[4]={-1,0,1,0};
  int vyk[4]={0,1,0,-1};
  while(cin>>W>>H,W+H!=0){
    int tx,ty,kx,ky;
    cin>>tx>>ty;
    cin>>kx>>ky;
    int ma[H+2][W+2];
    for(int i=0;i<H+2;i++)
      for(int j=0;j<W+2;j++)
	ma[i][j]=1;
    for(int i=1;i<H+1;i++)
      for(int j=1;j<W+1;j++)
	cin>>ma[i][j];
    queue<pair<pair<int,int>,int> >T;
    queue<pair<pair<int,int>,int> >K;
    T.push(make_pair(make_pair(tx,ty),0));
    K.push(make_pair(make_pair(kx,ky),0));
    bool flag=true;
    int ans;
    while(!(T.empty())&&!(K.empty())){
      if(counter>400)
	break;
      pair<pair<int,int>,int>nowt=T.front();
      pair<pair<int,int>,int>nowk=K.front();
      T.pop();K.pop();
      if(nowt.second>=100||nowk.second>=100){
	break;
      }
      if(nowt.second==nowk.second&&nowt.first.first==nowk.first.first&&
	 nowt.first.second==nowk.first.second){
	ans=nowt.second;
	flag=false;
	break;
      }
      for(int i=0;i<4;i++){
	if(ma[nowt.first.first+vxt[i]][nowt.first.second+vyt[i]]!=1)
	  T.push(make_pair(make_pair(nowt.first.first+vxt[i],nowt.first.second+vyt[i]),nowt.second+1));
	if(ma[nowk.first.first+vxk[i]][nowk.first.second+vyk[i]]!=1)
	  K.push(make_pair(make_pair(nowk.first.first+vxk[i],nowk.first.second+vyk[i]),nowk.second+1));
      }
      counter++;
    }
    if(flag)
      cout<<"NA"<<endl;
    else
      cout<<ans<<endl;
  }
  return 0;
}