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 := 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++
			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<queue>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
using namespace std;
int dy[]={1,-1,0,0};
int dx[]={0,0,1,-1};
// 構造体
struct P{
  int ty;
  int tx;
  int ky;
  int kx;
  int c;
  P(int ty,int tx,int ky,int kx,int c):ty(ty),tx(tx),ky(ky),kx(kx),c(c){}
};
int bfs(int ty,int tx,int ky,int kx);
int g[51][51];
int d[51][51][51][51]; // フラグ
int x,y;
int main(){
  int tx,ty;
  int kx,ky;
  while(1){
    cin >> x >> y;
    if(!x && !y)break;
    cin >> tx >> ty;
  cin >> kx >> ky;
  for(int i=0;i<y;i++){
    for(int j=0;j<x;j++){
      cin >> g[i][j];
    }
  }
  int ret = bfs( ty - 1 , tx - 1 , ky - 1 , kx - 1 );
  if(ret != -1){
    cout << ret << endl;
  }else {
    cout << "NA" << endl;
  }
    memset( d , 0 , sizeof(d) );
  }
}
int bfs(int ty,int tx,int ky,int kx){
  queue<P> que;
  que.push(P(ty,tx,ky,kx,0));
  d[ty][tx][ky][kx] = 1;

  while(!que.empty()){
    P p = que.front();que.pop();
    // 終了判定
    if(p.c >= 100)return -1;
    if(p.ty == p.ky && p.tx == p.kx)return p.c;
     for(int i=0;i<4;i++){
      int tty = p.ty + dy[i];
      int ttx = p.tx + dx[i];
      int kky = p.ky + (dy[i] * -1); // 　↓
      int kkx = p.kx + (dx[i] * -1); // 逆方向

      // 両方いけるとき
      if(0<=tty && tty<y && 0<=ttx && ttx<x){
        if(0<=kky && kky<y && 0<=kky && kkx<x){
          if(d[tty][ttx][kky][kkx] == 0  && g[tty][ttx] == 0 && g[kky][kkx] == 0){
            que.push(P(tty,ttx,kky,kkx,p.c+1));
            d[tty][ttx][kky][kkx] = 1;
          }
        }
      }
      // たかゆきくんだけいけるとき
      if(0<=tty && tty<y && 0<=ttx && ttx<x){
        if(0>kky || kky>=y || 0>kky || kkx>=x || g[kky][kkx] == 1){
          if(d[tty][ttx][p.ky][p.kx] == 0 && g[tty][ttx] == 0){
            que.push(P(tty,ttx,p.ky,p.kx,p.c+1));
            d[tty][ttx][p.ky][p.kx] = 1;
          }
        }
      }
      // 一之君だけいけるとき
       if(0<=kky && kky<y && 0<=kkx && kkx<x){
        if(0>tty || tty>=y || 0>tty || ttx>=x || g[tty][ttx] == 1){
          if(d[p.ty][p.tx][kky][kkx] == 0 && g[kky][kkx] == 0){
            que.push(P(p.ty,p.tx,kky,kkx,p.c+1));
            d[p.ty][p.tx][kky][kkx] = 1;
          }
        }
      }
    }
  }
  return -1;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <cstring>
#include <climits>
#include <algorithm>
#include <map>
using namespace std;

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

int X, Y;
int d[52][52];
int mintime[52][52][52][52];

void dfs(int tx, int ty, int kx, int ky, int t, int &mint) {
    if (tx == kx && ty == ky) {
        mint = min(t, mint);
        return ;
    }
    if (mint <= t) {
        return ;
    }
    mintime[tx][ty][kx][ky] = min(mintime[tx][ty][kx][ky], t);
    for (int i=0; i<4; ++i) {
        if (d[ty+dy[i]][tx+dx[i]] && d[ky-dy[i]][kx-dx[i]]) continue;
        int tx2 = tx, ty2 = ty;
        if ( ! d[ty+dy[i]][tx+dx[i]]) {
            tx2 += dx[i];
            ty2 += dy[i];
        }
        int kx2 = kx, ky2 = ky;
        if ( ! d[ky-dy[i]][kx-dx[i]]) {
            kx2 -= dx[i];
            ky2 -= dy[i];
        }
        if (t+1 < mintime[tx2][ty2][kx2][ky2]) {
            dfs(tx2, ty2, kx2, ky2, t+1, mint);
        }
    }
}

int main() {
    while (cin >> X >> Y, X) {
        int tx, ty, kx, ky;
        cin >> tx >> ty >> kx >> ky;
        for (int i=0; i<=Y+1; ++i) {
            for (int j=0; j<=X+1; ++j) {
                if (i==0 || i==Y+1 || j==0 || j==X+1) d[i][j] = 1;
                else cin >> d[i][j];
            }
        }
        for (int i=1; i<=Y; ++i) for (int j=1; j<=X; ++j) {
            for (int k=1; k<=Y; ++k) for (int l=1; l<=X; ++l) {
                mintime[i][j][k][l] = 101;
            }
        }
        int mint = 101;
        dfs(tx, ty, kx, ky, 0, mint);
        if (mint == 101) {
            cout << "NA" << endl;
        } else {
            cout << mint << endl;
        }
    }
    return 0;
}