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 ans <= now.Turn {
			continue
		}
		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<cstring>
#include<cstdlib>
#include<iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<stack>
using namespace std;


struct S{
  S(){};
  int tx,ty,kx,ky;
};
int X,Y;
S s;
vector<vector<int>> f;

bool input(){
  f.clear();
  s=S();
  cin>>X>>Y;
  if(X==0&&Y==0)return false;
  cin>>s.tx>>s.ty;
  cin>>s.kx>>s.ky;
  swap(s.tx,s.ty);
  swap(s.kx,s.ky);
  vector<int> kabe;
  for(int i=0;i<X+2;i++){
    kabe.push_back(1);
  }
  f.push_back(kabe);
  for(int i=0;i<Y;i++){
    vector<int> tt;
    tt.push_back(1);
    for(int j=0;j<X;j++){
      int tmp;
      cin>>tmp;
      tt.push_back(tmp);
    }
    tt.push_back(1);
    f.push_back(tt);
  }
  f.push_back(kabe);
  return true;
}

int vx[]={0,0,1,-1};
int vy[]={1,-1,0,0};
int used[50][50][50][50];
queue<S> q;
int bfs(S pos){
  memset(used,-1,(50*50*50*50));
  q = queue<S>();
  q.push(pos);
  used[pos.tx][pos.ty][pos.kx][pos.ky]=0;
  while(!q.empty()){
    S now = q.front();q.pop();
    if(used[now.tx][now.ty][now.kx][now.ky]>=100){
      return -1;
    }
    if(now.tx==now.kx&&now.ty==now.ky){
      return used[now.tx][now.ty][now.kx][now.ky];
    }
    for(int i=0;i<4;i++){
      S tmp = now;
      bool a,b;
      if(a=(f[tmp.tx+vx[i]][tmp.ty+vy[i]]!=1)){
        tmp.tx += vx[i];
        tmp.ty += vy[i];
      }
      if(b=(f[tmp.kx-vx[i]][tmp.ky-vy[i]]!=1)){
        tmp.kx -= vx[i];
        tmp.ky -= vy[i];
      }
      if((!(a||b))||(used[tmp.tx][tmp.ty][tmp.kx][tmp.ky]!=-1)){
        continue;
      }
      used[tmp.tx][tmp.ty][tmp.kx][tmp.ky]=used[now.tx][now.ty][now.kx][now.ky]+1;
      q.push(tmp);
    }
  }
  return -1;
}

int solve(){
  return bfs(s);
}

int main(){
  while(input()){
    int ans = solve();
    if(ans>=0){
      cout<<ans<<endl;
    }else{
      cout<<"NA"<<endl;
    }
  }
}

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 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 bfs(){
    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;
        int cost = data.cnt;
        if(cost > 100)break;
        if(memo[x1][y1][x2][y2] >= cost)continue;
        memo[x1][y1][x2][y2] = cost;
        if(x1 == x2 && y1 == y2){ans = cost;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), cost+1));
        }
    }

    return ans;
}

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 = bfs();
        if(a >= 100 || a == -1){
            cout << "NA" << endl;
        }else{
            cout << a << endl;
        }
    }
    return 0;    
}