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 <iostream>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>	// require sort next_permutation count __gcd reverse etc.
#include <cstdlib>	// require abs exit atof atoi 
#include <cstdio>		// require scanf printf
#include <functional>
#include <numeric>	// require accumulate
#include <cmath>		// require fabs
#include <climits>
#include <limits>
#include <cfloat>
#include <iomanip>	// require setw
#include <sstream>	// require stringstream 
#include <cstring>	// require memset
#include <cctype>		// require tolower, toupper
#include <fstream>	// require freopen
#include <ctime>		// require srand
#define rep(i,n) for(int i=0;i<(n);i++)
#define ALL(A) A.begin(), A.end()
#define INF 1<<30

using namespace std;

typedef long long ll;
typedef pair<int, int> P;
typedef pair<P,P> PP;
typedef pair<PP,int> PPi;

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

int grid[50][50];
bool vis[50][50][50][50];

/*
struct POS{
	int tx, ty, kx, ky, t;
	POS (int _tx, int _ty, int _kx, int _ky, int _t ) : tx(_tx), ty(_ty), kx(_kx), ky(_ky), t(_t) {}
//	bool operator>(const POS &a ) const{ return t > a.t; }
};
*/
int main()
{
//	cut here before submit 
//	freopen ("testcase.stray_twins", "r", stdin );
	int w, h;
	while (scanf ("%d %d", &w, &h ) && w && h ){
		memset (grid, 0, sizeof (grid ) );
//		memset (vis, false, sizeof (vis ) );

		rep (i, 50 ) rep (j, 50 ) rep (k, 50 ) rep (l, 50 ) vis[i][j][k][l] = false;
			
		int tx, ty, kx, ky;
		scanf ("%d %d %d %d", &tx, &ty, &kx, &ky );
		tx--;ty--;	kx--;ky--;
		rep (i, h ){
			rep (j, w ){
				scanf ("%d", &grid[i][j] );
			} // end rep
		} // end rep

		vis[tx][ty][kx][ky] = true;
//		priority_queue<POS, vector<POS>, greater<POS> > que;
		queue<PPi> que;
		que.push (PPi(PP(P(tx, ty ), P(kx, ky ) ), 0 ) );
		int res = INF;
		while (!que.empty() ){
			PPi curr = que.front(); que.pop();
			int ctx = curr.first.first.first;
			int cty = curr.first.first.second;
			int ckx = curr.first.second.first;
			int cky = curr.first.second.second; 
			int ct  = curr.second;
			rep (k, 4 ){
				int ntx = ctx + dx[k]; int nty = cty + dy[k];
				int nkx = ckx - dx[k]; int nky = cky - dy[k];
				if (ntx < 0 || ntx >= w || nty < 0 || nty >= h || grid[nty][ntx] ){
					ntx = tx; nty = ty;
				} // end if
				if (nkx < 0 || nkx >= w || nky < 0 || nky >= h || grid[nky][nkx] ){
					nkx = kx; nky = ky;
				} // end if
				if (vis[ntx][nty][nkx][nky] || ct + 1 >= 100 ) continue;
				if (ntx == nkx && nty == nky ){
					res = ct+1;
					goto ans;
				} // end if
				vis[ntx][nty][nkx][nky] = true;
				que.push (PPi(PP(P(ntx, nty ), P(nkx, nky ) ), ct+1 ) );
			} // end rep
		} // end while
ans:;
		if (res != INF ){
			printf ("%d\n", res );
		}else{
			printf ("NA\n" );
		} // end if

	} // end loop
		
	return 0;
}

C++: #include <iostream>
#include <vector>
#include <queue>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)

int dx[] = {-1,0,1,0};
int dy[] = {0,1,0,-1};
struct NODE{
	int x1,y1,x2,y2,d;
	NODE(int a,int b,int c,int D,int e){
		x1 = a , y1 = b , x2 = c , y2 = D , d = e;
	}
};
bool done[52][52][52][52] = {0};
bool data[52][52];
int main(){
	int W,H;
	while(cin >> W >> H , W){
		int a,b,c,d;
		cin >> a >> b >> c >> d;
		rep(i,52)rep(j,52)data[i][j] = true;
		rep(i,H)rep(j,W)cin >> data[i+1][j+1];
		queue<NODE> Q;
		Q.push(NODE(a,b,c,d,0));
		int ans = -1;
		rep(i,52)rep(j,52)rep(k,52)rep(l,52)
			done[i][j][k][l] = 0;
		
		while(Q.size()){
			NODE q = Q.front(); Q.pop();
			if(q.d >= 100) break;
			if(done[q.y1][q.x1][q.y2][q.x2])continue;
			else done[q.y1][q.x1][q.y2][q.x2] = true;
			
			if(q.x1 == q.x2 && q.y1 == q.y2){
				ans = q.d;
				break;
			}
			rep(i,4){
				int A = q.x1 + dx[i] , B = q.y1 + dy[i];
				int C = q.x2 - dx[i] , D = q.y2 - dy[i];
				if(data[B][A])A = q.x1 , B = q.y1;
				if(data[D][C])C = q.x2 , D = q.y2;
				Q.push(NODE(A,B,C,D,q.d+1));
			}
		}
		if(~ans){
			cout << ans << endl;
		}else{
			cout << "NA" << endl;
		}
	}
}