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 v, ok := memo[now.Person]; ok && v <= now.Turn {
			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>
#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() {
	int W, H;
	bool d[52][52];
	while (true) {
		map<state, bool> m;
		queue<state> q;
		cin >> W >> H;
		if (W == 0)break;
		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;
		q.push(num);
		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[copy]) {
					m[copy] = true;
					copy.time = num.time + 1;
					q.push(copy);
				}
			}
			if (q.empty()) {
				cout << "NA" << endl;
				break;
			}
		}
	}
	return 0;
}

C++: #include<bits/stdc++.h>
#define r(i,n) for(int i=0;i<n;i++)
using namespace std;
#define mk make_pair
#define f first
#define s second
typedef pair<int,int> P;
int a[51][51],ax,bx,ay,by;
int dx1[]={1,0,-1,0};
int dy1[]={0,1,0,-1};
int dx2[]={-1,0,1,0};
int dy2[]={0,-1,0,1};
bool used[100000000];
int gethash(P q,P w){
  return q.f+q.s*52+w.f*52*52+w.s*52*52*52;
}
int main(){
  int w,h;
  while(cin>>w>>h,w){
    memset(used,0,sizeof(used));
    cin>>ax>>ay>>bx>>by;ax--,ay--,bx--,by--;
    r(i,h)r(j,w)cin>>a[i][j];
    used[gethash(P(ay,ax),P(by,bx))]=1;
    queue<pair<int,pair<pair<int,int>,pair<int,int> > > >q;
    q.push(mk(0,mk(mk(ay,ax),mk(by,bx))));
    while(!q.empty()){
      pair<int,pair<pair<int,int>,pair<int,int> > >p=q.front();q.pop();
      P p1=p.s.f,p2=p.s.s;
      if(p1==p2){
	cout<<p.f<<endl;
	goto L;
      }
      r(i,4){
	int x1=p1.s+dx1[i],x2=p2.s+dx2[i],y1=p1.f+dy1[i],y2=p2.f+dy2[i];
	if(x1<0||x1>=w)x1=p1.s;
	if(x2<0||x2>=w)x2=p2.s;
	if(y1<0||y1>=h)y1=p1.f;
	if(y2<0||y2>=h)y2=p2.f;
	if(a[y1][x1])x1=p1.s,y1=p1.f;
	if(a[y2][x2])x2=p2.s,y2=p2.f;
	if(!used[gethash(P(y1,x1),P(y2,x2))]){
	  used[gethash(P(y1,x1),P(y2,x2))]=1;
	  q.push(mk(p.f+1,mk(mk(y1,x1),mk(y2,x2))));
	}
      }
    }
    cout<<"NA"<<endl;L:;
  }
}

C++: #include<bits/stdc++.h>
#define P pair<int,int>
using namespace std;

int dx[4] = { -1,0,0,1 }, dy[4] = { 0,-1,1,0 };
int main() {
	int a, b;
	while (cin >> b>>a, a | b) {
		int c, d, e, f;
		cin >> c >> d >> e >> f;
		c--; d--; e--; f--;
		bool ba[50][50];
		int k[50][50];
		memset(k, -1, sizeof(k));
		for (int g = 0; g < a; g++) {
			for (int h = 0; h < b; h++) {
				cin >> ba[g][h];
			}
		}
		if ((((c - e) & 1) == 0) && (((d - f) & 1) == 0)) {
			queue<P>Q;
			if (!ba[c][d] && !ba[e][f]) {
				Q.push(P(c, d));
				k[c][d] = 0;
			}
			while (Q.size()) {
				P o = Q.front(); Q.pop();
				for (int i = 0; i < 4; i++) {
					int x = dx[i],y=dy[i];
						if (o.first + x >= 0 && o.first + x < a&&o.second + y >= 0 && o.second + y < b) {
							if (c + e - (o.first + x) >= 0 && c + e - (o.first + x) < a&&d + f - (o.second + y) >= 0 && d + f - (o.second + y) < b) {
								if (!ba[o.first + x][o.second + y] && !ba[c + e - (o.first + x)][d + f - (o.second + y)] && k[o.first + x][o.second + y] == -1) {
									Q.push(P(o.first + x, o.second + y));
									k[o.first + x][o.second + y] = k[o.first][o.second] + 1;
								}
							}
						}
				}
			}
	        if(k[(c+e)/2][(d+f)/2]==-1)puts("NA");
else  cout<<k[(c+e)/2][(d+f)/2]<<endl;
		}
		else puts("NA");
	}
}