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 <cstdio>
#include <cstdlib>
#include <cstring>
#include <utility>
#include <queue>
#include <algorithm>
using namespace std;
typedef pair<int,int> P1;
typedef pair<P1,P1> P2;
typedef pair<int,P2> P3;
int d[50][51];
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
bool used[50][50][50][50];
int main() {
	int X,Y;
	while(scanf("%d %d",&X,&Y),X) {
		memset(used,0,sizeof(used));
		int tx,ty,kx,ky;
		scanf("%d %d",&tx,&ty); tx--;ty--;
		scanf("%d %d",&kx,&ky); kx--;ky--;
		for(int i=0;i<Y;i++) {
			for(int j=0;j<X;j++) scanf("%d",&d[i][j]);
		}
		queue<P3> Q;
		Q.push(P3(0,P2(P1(tx,ty),P1(kx,ky))));
		used[tx][ty][kx][ky]=1;
		bool NA=1;
		while(!Q.empty()) {
			P3 p3=Q.front();Q.pop();
			int tx=p3.second.first.first;
			int ty=p3.second.first.second;
			int kx=p3.second.second.first;
			int ky=p3.second.second.second;
			if(p3.first>=100) break;
			if(tx==kx&&ty==ky) {
				printf("%d\n",p3.first);
				NA=0;
				break;
			}
			for(int i=0;i<4;i++) {
				int ntx=tx+dx[i],nty=ty+dy[i];
				int nkx=kx-dx[i],nky=ky-dy[i];
				if(0>ntx||ntx>=X||0>nty||nty>=Y||d[nty][ntx]) {
					ntx=tx,nty=ty;
				}
				if(0>nkx||nkx>=X||0>nky||nky>=Y||d[nky][nkx]) {
					nkx=kx,nky=ky;
				}
				if(!used[ntx][nty][nkx][nky]) {
					used[ntx][nty][nkx][nky]=1;
					Q.push(P3(p3.first+1,P2(P1(ntx,nty),P1(nkx,nky))));
				}
			}
		}
		if(NA) printf("NA\n");
	}
}

C++: #include<iostream>
#include<queue>
struct D{int t,u,k,l,c;};main(){for(int X,Y,t,u,k,l,d[50][50],a[4]={1,0,-1,0};std::cin>>X>>Y>>t>>u>>k>>l,X;~k?printf("%d\n",k):puts("NA")){std::queue<D>q;D p={t-1,u-1,k-1,l-1,0},r;q.push(p);for(u=0;u<Y;u++)for(t=0;t<X;t++)std::cin>>d[t][u];bool v[50][50][50][50]={0};for(k=-1;q.size();){p=q.front();q.pop();if(p.t==p.k&&p.u==p.l){k=p.c;break;}v[p.t][p.u][p.k][p.l]=1;for(t=4;t-->0;){r=p;r.t+=a[t];r.u+=a[(t+3)%4];r.k+=a[(t+2)%4];r.l+=a[(t+1)%4];r.c++;if(r.t<0|X<=r.t|r.u<0|Y<=r.u|d[r.t][r.u]){r.t=p.t;r.u=p.u;}if(r.k<0|X<=r.k|r.l<0|Y<=r.l|d[r.k][r.l]){r.k=p.k;r.l=p.l;}if(!v[r.t][r.u][r.k][r.l])q.push(r);v[r.t][r.u][r.k][r.l]=1;}}}}

C++: #include<stdio.h>
#include<iostream>
#include<queue>
#include<string.h>
using namespace std;
struct Y{
int hx,hy,rx,ry,tim;
};
int c[51][51][51][51];
int main(){
int n,w,h,i,j,a[2]={1,-1},b[2];
Y e;
while(cin>>w>>h&&w!=0&&h!=0){
int mp[52][52]={0};
queue<Y> q;
	cin>>e.hx>>e.hy>>e.rx>>e.ry;
	e.tim=0;
	q.push(e);
	memset(c,0,sizeof(c));
	for(i=0;i<=h+1;i++){
		mp[i][0]=1;
		mp[i][w+1]=1;
	}
	for(i=0;i<=w+1;i++){
		mp[0][i]=1;
		mp[h+1][i]=1;
	}
	for(i=1;i<=h;i++){
		for(j=1;j<=w;j++){
			cin>>mp[j][i];
		}
	}
	while(!q.empty()){
		e=q.front();
		q.pop();
		c[e.hy][e.hx][e.ry][e.rx]=1;
		if(e.tim>=100||e.hx==e.rx&&e.hy==e.ry)break;
		e.tim++;
		for(i=0;i<2;i++){
			if(mp[e.hy+a[i]][e.hx]!=1&&c[e.hy+a[i]][e.hx][e.ry-a[i]][e.rx]==0&&mp[e.ry-a[i]][e.rx]!=1||mp[e.ry-a[i]][e.rx]!=1&&c[e.hy][e.hx][e.ry-a[i]][e.rx]==0&&mp[e.hy+a[i]][e.hx]==1||mp[e.hy+a[i]][e.hx]!=1&&mp[e.ry-a[i]][e.rx]==1&&c[e.hy+a[i]][e.hx][e.ry][e.rx]==0){
				b[0]=0;																										
				b[1]=0;																																		
				if(mp[e.hy+a[i]][e.hx]!=1){																											
					e.hy+=a[i];																																			
					b[0]=1;																																					
				}																																													
				if(mp[e.ry-a[i]][e.rx]!=1){																																										
					e.ry-=a[i];																																		
					b[1]=1;																																																														
				}		
				c[e.hy][e.hx][e.ry][e.rx]=1;																																																																																																																
				q.push(e);																											
				if(b[0]==1)e.hy-=a[i];																														
				if(b[1]==1)e.ry+=a[i];																											
			}																																																												
			if(mp[e.hy][e.hx+a[i]]!=1&&mp[e.ry][e.rx-a[i]]!=1&&c[e.hy][e.hx+a[i]][e.ry][e.rx-a[i]]==0||mp[e.hy][e.hx+a[i]]!=1&&c[e.hy][e.hx+a[i]][e.ry][e.rx]==0&&mp[e.ry][e.rx-a[i]]==1||mp[e.ry][e.rx-a[i]]!=1&&mp[e.hy][e.hx+a[i]]==1&&c[e.hy][e.hx][e.ry][e.rx-a[i]]==0){
				b[0]=0;
				b[1]=0;
				if(mp[e.hy][e.hx+a[i]]!=1){
					e.hx+=a[i];
					b[0]=1;
				}
				if(mp[e.ry][e.rx-a[i]]!=1){
					e.rx-=a[i];
					b[1]=1;
				}
				c[e.hy][e.hx][e.ry][e.rx]=1;
				q.push(e);
				if(b[0]==1)e.hx-=a[i];
				if(b[1]==1)e.rx+=a[i];
			}
		}
		e.tim--;
	}
	if(e.hy==e.ry&&e.hx==e.rx)cout<<e.tim<<endl;
	else printf("NA\n");
}
return 0;
}