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++: // 2018/07/04 Tazoe

#include <iostream>
#include <queue>
#include <map>
using namespace std;

class Point2{
public:
	int tx;
	int ty;
	int kx;
	int ky;
};

int mk(Point2 p)		// キーを生成
{
	return (((p.tx-1)*50+(p.ty-1))*50+(p.kx-1))*50+(p.ky-1);
}

int main()
{
	while(true){
		int W, H;
		cin >> W >> H;

		if(W==0 && H==0)
			break;

		Point2 p;
		cin >> p.tx >> p.ty;
		cin >> p.kx >> p.ky;

		int d[52][52];
		for(int y=0; y<=H+1; y++){
			for(int x=0; x<=W+1; x++){
				d[y][x] = 1;			// 番兵
			}
		}

		for(int y=1; y<=H; y++){
			for(int x=1; x<=W; x++){
				cin >> d[y][x];
			}
		}

		queue<Point2> que;		// キュー
		que.push(p);

		map<int, int> n;			// マップ（時間）
		n[mk(p)] = 0;

		while(true){
			if(que.empty()){			// 出会うことができない場合
				cout << "NA" << endl;
				break;
			}

			p = que.front();
			que.pop();

			if(n[mk(p)]>=100){		// 100以上の時間を要する場合
				cout << "NA" << endl;
				break;
			}

			if(p.tx==p.kx && p.ty==p.ky){		// 2人が出会う
				cout << n[mk(p)] << endl;
				break;
			}

			Point2 q;

			// 東
			q = p;
			if(d[q.ty][q.tx+1]==0){
				q.tx = q.tx+1;
			}
			if(d[q.ky][q.kx-1]==0){
				q.kx = q.kx-1;
			}
			if(n.find(mk(q))==n.end()){
				que.push(q);
				n[mk(q)] = n[mk(p)]+1;
			}

			// 西
			q = p;
			if(d[q.ty][q.tx-1]==0){
				q.tx = q.tx-1;
			}
			if(d[q.ky][q.kx+1]==0){
				q.kx = q.kx+1;
			}
			if(n.find(mk(q))==n.end()){
				que.push(q);
				n[mk(q)] = n[mk(p)]+1;
			}

			// 南
			q = p;
			if(d[q.ty+1][q.tx]==0){
				q.ty = q.ty+1;
			}
			if(d[q.ky-1][q.kx]==0){
				q.ky = q.ky-1;
			}
			if(n.find(mk(q))==n.end()){
				que.push(q);
				n[mk(q)] = n[mk(p)]+1;
			}

			// 北
			q = p;
			if(d[q.ty-1][q.tx]==0){
				q.ty = q.ty-1;
			}
			if(d[q.ky+1][q.kx]==0){
				q.ky = q.ky+1;
			}
			if(n.find(mk(q))==n.end()){
				que.push(q);
				n[mk(q)] = n[mk(p)]+1;
			}
		}
	}

	return 0;
}

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