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(101)
	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]
			}
			next.Turn += 1
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				pq = append(pq, 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>
using namespace std;
struct pos { int td,kd; };
int dm[50][50],tc[2500][2500],pn[2],g;
pos p[2][3000000];

int main() {
	int ax,ay,i,j,t,x,y,tx,ty,kx,ky,tx2,ty2,kx2,ky2,dx[4]={1,0,-1,0},dy[4]={0,-1,0,1};
	while(cin >> x >> y && x>0) {
		pn[0]=1; g=0;
		for (i=0;i<x*y;i++) for (j=0;j<x*y;j++) tc[i][j]=0;
		cin >> tx >> ty >> kx >> ky;
		ax=(ty-1)*x+tx-1; ay=(ky-1)*x+kx-1; tc[ax][ay]=1; p[g][0].td=ax; p[g][0].kd=ay;
		for (i=0;i<y;i++) for (j=0;j<x;j++) cin >> dm[i][j];
		for (t=1;t<101;t++) {
			pn[1-g]=0;
			for (i=0;i<pn[g];i++) {
				tx=p[g][i].td % x; ty=p[g][i].td/x;
				kx=p[g][i].kd % x; ky=p[g][i].kd/x;
				for (j=0;j<4;j++) {
					ax=tx+dx[j]; ay=ty+dy[j];
					if (ax>=0 && ax<x && ay>=0 && ay<y) if (dm[ay][ax]==0) { tx2=ax; ty2=ay;}
					ax=kx-dx[j]; ay=ky-dy[j];
					if (ax>=0 && ax<x && ay>=0 && ay<y) if (dm[ay][ax]==0) { kx2=ax; ky2=ay;}
					if (tx2==kx2 && ty2==ky2) break;
					ax=ty2*x+tx2; ay=ky2*x+kx2;
					if (tc[ax][ay]==0) { tc[ax][ay]=1; p[1-g][pn[1-g]].td=ax; p[1-g][pn[1-g]].kd=ay; pn[1-g]++;}
				}
				if (j<4) break;
			}
			if (j<4) break;
			g=1-g;
		}
		if (j<4 && t<101) cout << t << endl; else cout << "NA" << endl;
	} 
	return 0;
}

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

using namespace std ;

struct ST
{
	int tx ,ty ;
	int kx ,ky ;
	int cnt ;
	ST( int a ,int s ,int d ,int f ,int g ) : tx( a ) ,ty( s ) ,kx( d ) ,ky( f ) ,cnt( g ){}
} ;

int mx[ 4 ] = { 1 ,0 ,0 ,-1 } ;
int my[ 4 ] = { 0 ,1 ,-1 ,0 } ;
int map[ 50 ][ 50 ] ;

int w ,h ;
int tx ,kx ;
int ty ,ky ;

void ans()
{
	queue< ST > que ;
	bool came[ 50 ][ 50 ][ 50 ][ 50 ] = { false } ;
	que.push( ST( tx - 1 ,ty - 1 ,kx - 1 ,ky - 1 ,0 ) ) ;
	came[ tx - 1 ][ ty - 1 ][ kx - 1 ][ ky - 1 ] = true ;
	while( ! que.empty() )
	{
		ST st = que.front() ;
		if( st.tx == st.kx && st.ty == st.ky )
		{
			cout << st.cnt << endl ;
			return ;
		}
		else if( st.cnt >= 100 )
		{
			break ;
		}
		que.pop() ;
		for( int i = 0 ; i < 4 ; i++ )
		{
			int j = 3 - i ;
			tx = st.tx + mx[ i ] ;
			kx = st.kx + mx[ j ] ;
			ty = st.ty + my[ i ] ;
			ky = st.ky + my[ j ] ;
			if( tx < 0 || tx >= w || ty < 0 || ty >= h || map[ ty ][ tx ] == 1 )
			{
				tx = st.tx ;
				ty = st.ty ;
			}
			if( kx < 0 || kx >= w || ky < 0 || ky >= h || map[ ky ][ kx ] == 1 )
			{
				kx = st.kx ;
				ky = st.ky ;
			}
			if( came[ tx ][ ty ][ kx ][ ky ] == false )
			{
				que.push( ST( tx ,ty ,kx ,ky ,st.cnt + 1 ) ) ;
				came[ tx ][ ty ][ kx ][ ky ] = true ;
			}
		}
	}
	cout << "NA" << endl ;
}

int main()
{
	while( cin >> w >> h ,h )
	{
		cin >> tx >> ty ;
		cin >> kx >> ky ;
		for( int i = 0 ; i < h ; i++ )
		{
			for( int j = 0 ; j < w ; j++ )
			{
				cin >> map[ i ][ j ] ;
			}
		}
		ans() ;
	}
}

C++: #include<stdio.h>
#include<algorithm>
#include<queue>
using namespace std;
int m[50][50];
int dx[]={1,-1,0,0};
int dy[]={0,0,1,-1};
int bfs[50][50][50][50];
struct wolf{
	int a,b,c,d;
	wolf(int A,int B,int C,int D){
		a=A;
		b=B;
		c=C;
		d=D;
	}
};
int main(){
	int a,b;
	while(scanf("%d%d",&a,&b),a+b){
		int r1,r2,c1,c2;
		scanf("%d%d%d%d",&r1,&c1,&r2,&c2);
		for(int i=0;i<b;i++)
			for(int j=0;j<a;j++)
				scanf("%d",&m[i][j]);
		int inf=999999999;
		for(int i=0;i<b;i++)
			for(int j=0;j<a;j++)
				for(int k=0;k<b;k++)
					for(int l=0;l<a;l++)
						bfs[i][j][k][l]=inf;
		r1--;c1--;r2--;c2--;
		bfs[r1][c1][r2][c2]=0;
		queue<wolf> Q;
		Q.push(wolf(r1,c1,r2,c2));
		while(Q.size()){
			wolf at=Q.front();
			Q.pop();
			if(bfs[at.a][at.b][at.c][at.d]==99)continue;
			for(int i=0;i<4;i++){
				int s1=at.a+dx[i];
				int t1=at.b+dy[i];
				int s2=at.c-dx[i];
				int t2=at.d-dy[i];
				if(s1<0||s1>=b||m[s1][t1])s1-=dx[i];
				if(t1<0||t1>=a||m[s1][t1])t1-=dy[i];
				if(s2<0||s2>=b||m[s2][t2])s2+=dx[i];
				if(t2<0||t2>=a||m[s2][t2])t2+=dy[i];
				if(bfs[s1][t1][s2][t2]==inf){
					bfs[s1][t1][s2][t2]=bfs[at.a][at.b][at.c][at.d]+1;
					Q.push(wolf(s1,t1,s2,t2));
				}
			}
		}
		int ret=inf;
		for(int i=0;i<b;i++)for(int j=0;j<a;j++)ret=min(ret,bfs[i][j][i][j]);if(ret==inf)printf("NA\n");else printf("%d\n",ret);
	}
}