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 := &Status{}
		now = pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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<stdio.h>
#define STACK_MAX 1000
int sptt = -1,sptk=-1;
typedef struct {
    int x;
	int y;
} stack_t;
stack_t t[STACK_MAX],k[STACK_MAX];
int tpush( int vx, int vy ) {
    if( sptt >= STACK_MAX-1 ) return -1;

    sptt++;
   t[sptt].x = vx;
   t[sptt].y = vy;
    return 0;
}
int tpop( int *vx, int *vy ) {
    if( sptt < 0 ) return -1;
    *vx = t[sptt].x;
	*vy = t[sptt].y;
    sptt--;
    return 0;
}
int kpush( int vx, int vy ) {
    if( sptk >= STACK_MAX-1 ) return -1;

    sptk++;
   k[sptk].x = vx;
   k[sptk].y = vy;
    return 0;
}
int kpop( int *vx, int *vy ) {
    if( sptk < 0 ) return -1;
    *vx = k[sptk].x;
	*vy = k[sptk].y;
    sptk--;
    return 0;
}
int main(){
	while(1){
		int x,y,d[50][50],i,j,tlx[4]={0,1,0,-1},tly[4]={-1,0,1,0},cnt=0,tfx,tfy,kfx,kfy,klx[4]={0,-1,0,1},kly[4]={1,0,-1,0},tc[50][50]={},kc[50][50]={},tm[50][50]={},km[50][50]={},mx,my,f=0,h[50][50]={};
		scanf("%d %d",&mx,&my);
			if(mx==0&&my==0){
				break;
			}
		scanf("%d %d",&tfx,&tfy);
		scanf("%d %d",&kfx,&kfy);
		tpush(tfx-1,tfy-1);
		kpush(kfx-1,kfy-1);
		for(i=0;i<my;i++){
			for(j=0;j<mx;j++){
					scanf("%d",&d[i][j]);
			}
		}
		while(1){
			while(1){
				tpop(&tfx,&tfy);
				kpop(&kfx,&kfy);
				if(tfx!=1000&&tfy!=1000&&kfx!=1000&&kfy!=1000){
					break;
				}
			}
			if(tfx==kfx&&tfy==kfy){
				break;
			}
			tm[tfy][tfx]=1;
			km[kfy][kfx]=1;
			for(i=0;i<4;i++){
				if(d[tfy+tly[i]][tfx+tlx[i]]==0&&tm[tfy+tly[i]][tfx+tlx[i]]==0&&(tfx+tlx[i])>=0&&(tfx+tlx[i])<mx&&(tfy+tly[i])>=0&&(tfy+tly[i])<my){
					tpush(tfx+tlx[i],tfy+tly[i]);
					tc[tfy+tly[i]][tfx+tlx[i]]=tc[tfy][tfx]+1;
					h[tfy+tly[i]][tfx+tlx[i]]=1;
				}
				else{
					tpush(1000,1000);
				}
				if(d[kfy+kly[i]][kfx+klx[i]]==0&&km[kfy+kly[i]][kfx+klx[i]]==0&&(kfx+klx[i])>=0&&(kfx+klx[i])<mx&&(kfy+kly[i])>=0&&(kfy+kly[i])<my){
					kpush(kfx+klx[i],kfy+kly[i]);
					kc[kfy+kly[i]][kfx+klx[i]]=kc[kfy][kfx]+1;
					h[kfy+kly[i]][kfx+klx[i]]=1;
				}
				else{
					kpush(1000,1000);
				}
			}
			f=0;
			for(i=0;i<my;i++){
				for(j=0;j<mx;j++){
					if(d[i][j]==0&&h[i][j]==0){
						f=1;
					}
				}
			}
			if(f==0){
				break;
			}
		}
		if(tfx==kfx&&tfy==kfy){
				printf("%d\n",tc[tfy][tfx]);
		}
		else{
			printf("NA\n");
		}
	}
	return 0;
}

C++: #include <cstdio>
#include <queue>
#include <string.h>
using namespace std;

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

inline int enc(int y,int x){
    return 52*y+x;
}

inline int enc2(int ty, int tx, int ky, int kx){
    return enc(ty,tx)*52*52 + enc(ky,kx);
}

int main(){
    int w,h,tx,ty,kx,ky;
    static char board[52][52];
    static char dist[52*52*52*52];
    while(scanf("%d%d",&w,&h),w){
        queue< pair<int,int> > Q;
        scanf("%d%d%d%d",&tx,&ty,&kx,&ky);
        for(int i=0; i<52; i++)
            for(int j=0; j<52; j++)
                board[i][j] = 1;
        for(int i=1; i<=h; i++)
            for(int j=1; j<=w;j++){
                int x;
                scanf("%d",&x);
                board[i][j] = x;
            }
        memset(dist,101,sizeof(dist));
        if(enc(ty,tx)==enc(ky,kx)){
            printf("%d\n",0);
            goto end;
        }

        dist[enc2(ty,tx,ky,kx)] = 0;
        for(int k=0; k<4; k++){
            int nty = ty + dy[k],
                ntx = tx + dx[k],
                nky = ky - dy[k],
                nkx = kx - dx[k];
            if(board[nty][ntx]) nty = ty, ntx = tx;
            if(board[nky][nkx]) nky = ky, nkx = kx;
            if(enc(nty,ntx)==enc(nky,nkx)){
                printf("%d\n",1);
                goto end;
            }
            int p = enc2(nty,ntx,nky,nkx);
            if(1 < dist[p]){
                dist[p] = 1;
                Q.push( make_pair(p,2) );
            }
        }
        while(!Q.empty()){
            ty = (Q.front().first/(52*52))/52;
            tx = (Q.front().first/(52*52))%52;
            ky = (Q.front().first%(52*52))/52;
            kx = (Q.front().first%(52*52))%52;
            int d = Q.front().second;
            if(d > 100) break;
            Q.pop();
            for(int k=0; k<4; k++){
               int nty = ty + dy[k],
                   ntx = tx + dx[k],
                   nky = ky - dy[k],
                   nkx = kx - dx[k];
               if(board[nty][ntx]) nty = ty, ntx = tx;
               if(board[nky][nkx]) nky = ky, nkx = kx;
               if(enc(nty,ntx)==enc(nky,nkx)){
                    printf("%d\n",d);
                    goto end;
               }
               int p = enc2(nty,ntx,nky,nkx);
               if(d < dist[p]){
                   dist[p] = d;
                   Q.push( make_pair(p,d+1) );
               }
           }
        }
        printf("NA\n");
end:;
    }
}