Go: package main

import (
	"container/heap"
	"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.Push(&pq, start)
	dx := []int64{0, 1, 0, -1}
	dy := []int64{1, 0, -1, 0}
	memo := make(map[PersonPosition]struct{}, 0)
	for pq.Len() > 0 {
		heap.Init(&pq)
		now := heap.Pop(&pq).(*Status)
		if now.Person.Distance() == 0 {
			fmt.Println(now.Turn)
			return
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = struct{}{}
		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)
			}
		}
	}
	fmt.Println("NA")
}

func main() {
	var h, w int64
	for {
		fmt.Scan(&h, &w)
		if h == 0 && w == 0 {
			break
		}
		solve(h, w)
	}
}

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

#define MAX_X 1000
#define MAX_Y 1000

using namespace std;

typedef pair<int,int> P;
typedef pair<P,P> PP;

int d[MAX_Y][MAX_X][MAX_Y][MAX_X];

int tx,ty,kx,ky,ntx,nty,nkx,nky;
int ans;

short maze[MAX_Y][MAX_X];
int Y,X;

int dx[4]={1,0,-1,0},dy[4]={0,1,0,-1};

bool bfs(){
	queue<PP> que;
	map<PP,int> mat;
	que.push(make_pair(make_pair(ty,tx),make_pair(ky,kx)));
	
	mat[que.front()]=0;
	while (que.size()) {
		PP p=que.front();
		que.pop();
		if (p.first.first==p.second.first&&p.first.second==p.second.second) {
			ans=d[p.first.first][p.first.second][p.second.first][p.second.second];
			return true;
		}
		if (d[p.first.first][p.first.second][p.second.first][p.second.second]>=100) {
			return false;
		}
		if (mat[que.front()]) {
			continue;
		}
		for (int i=0; i<4; i++) {
			ntx=p.first.second+dx[i],nty=p.first.first+dy[i],nkx=p.second.second+dx[i]*(-1),nky=p.second.first+dy[i]*(-1);
			int flag=2;
			if (!(0<=ntx&&ntx<X&&0<=nty&&nty<Y&&maze[nty][ntx]!=1)){
				flag-=1;
				ntx=p.first.second;
				nty=p.first.first;
			}
			if (!(0<=nkx&&nkx<X&&0<=nky&&nky<Y&&maze[nky][nkx]!=1)) {
				flag-=1;
				nkx=p.second.second;
				nky=p.second.first;
			}
			if (flag!=0) {
				que.push(make_pair(make_pair(nty,ntx),make_pair(nky,nkx)));
				d[nty][ntx][nky][nkx]=d[p.first.first][p.first.second][p.second.first][p.second.second]+1;
			}
			mat[que.front()] = d[nty][ntx][nky][nkx];
		}
	}
	return false;
}

int main(){
	while (cin>>X>>Y&&X&&Y) {
		cin>>tx>>ty>>kx>>ky;
		tx-=1;
		ty-=1;
		kx-=1;
		ky-=1;
		for (int i=0; i<Y; i++) {
			for (int j=0; j<X; j++) {
				cin>>maze[i][j];
			}
		}
		if(bfs()){
			cout << ans <<endl;
		}
		else {
			cout << "NA" << endl;
		}
	}
}

C++: #include <cstdio>
#include <cstring>
#include <queue>
using namespace std;

struct S {
	int tx,ty;
	int kx,ky;
	int turn;
	S::S(int tx,int ty,int kx,int ky,int turn);
};

S::S(int _tx,int _ty,int _kx,int _ky,int _turn) {
	tx=_tx;
	ty=_ty;
	kx=_kx;
	ky=_ky;
	turn=_turn;
}

bool d[50][50];
bool vst[50][50][50][50];
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};

int main() {
	int X,Y;
	int tx,ty;
	int kx,ky;
	while(scanf("%d %d",&X,&Y),X||Y) {
		scanf("%d %d",&tx,&ty);
		scanf("%d %d",&kx,&ky);
		for(int j=0;j<Y;j++) {
			for(int i=0;i<X;i++) {
				scanf("%d",&d[i][j]);
			}
		}
		tx--;ty--;kx--;ky--;
		queue<S> q;
		bool ok=false;
		q.push(S(tx,ty,kx,ky,0));
		memset(vst,false,sizeof(vst));
		vst[tx][ty][kx][ky]=true;
		while(!q.empty()) {
			S s=q.front();q.pop();
			if(s.turn>=100) break;
			if(s.tx==s.kx&&s.ty==s.ky) {
				printf("%d\n",s.turn);
				ok=true;
				break;
			}
			for(int i=0;i<4;i++) {
				int ntx=s.tx+dx[i],nty=s.ty+dy[i];
				int nkx=s.kx-dx[i],nky=s.ky-dy[i];
				if(0>ntx||ntx>=X||0>nty||nty>=Y||d[ntx][nty]) {
					ntx-=dx[i],nty-=dy[i];
				}
				if(0>nkx||nkx>=X||0>nky||nky>=Y||d[nkx][nky]) {
					nkx+=dx[i],nky+=dy[i];
				}
				if(!vst[ntx][nty][nkx][nky]) {
					vst[ntx][nty][nkx][nky]=true;
					q.push(S(ntx,nty,nkx,nky,s.turn+1));
				}
			}
		}
		if(!ok) printf("NA\n");
	}
	return 0;
}

C++: #include<iostream>
#include<queue>
#include<map>
using namespace std;
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
class state {
public:
	int tx;
	int ty;
	int kx;
	int ky;
	int time;
	bool operator < (const state &s)const {
		if (ty != s.ty)return ty < s.ty;
		if (tx != s.tx)return tx < s.tx;
		if (ky != s.ky)return ky < s.ky;
		if (kx != s.kx)return kx < s.kx;
		return false;
	}
};
int main() {
	while (true) {
		int W, H;
		cin >> W >> H;
		if (W == 0 && H == 0)
			break;
		bool d[52][52];
		for (int i = 0; i < H + 2; i++) {
			for (int j = 0; j < W + 2; j++) {
				d[i][j] = 1;
			}
		}
		state num;
		cin >> num.tx >> num.ty >> num.kx >> num.ky;
		for (int i = 1; i < H + 1; i++) {
			for (int j = 1; j < W + 1; j++) {
				cin >> d[j][i];
			}
		}
		num.time = 0;
		queue<state> q;
		q.push(num);
		map<state, bool> m;
		m[num] = true;
		while (true) {
			num = q.front();
			q.pop();
			if (num.time >= 100) {
				cout << "NA" << endl;
				break;
			}
			if (num.tx == num.kx && num.ty == num.ky) {
				cout << num.time << endl;
				break;
			}
			for (int i = 0; i < 4; i++) {
				state copy;
				copy.tx = num.tx + dx[i];
				copy.ty = num.ty + dy[i];
				copy.kx = num.kx - dx[i];
				copy.ky = num.ky - dy[i];
				if (d[copy.tx][copy.ty]) {
					copy.tx = num.tx;
					copy.ty = num.ty;
				}
				if (d[copy.kx][copy.ky]) {
					copy.kx = num.kx;
					copy.ky = num.ky;
				}
				if (m.find(copy)==m.end()) {
					copy.time = num.time + 1;
					q.push(copy);
					m[copy] = true;
				}
			}
			if (q.empty()) {
				cout << "NA" << endl;
				break;
			}
		}
	}
	return 0;
}