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.Init(&pq)
	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 {
		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 <vector>
#include <queue>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)

int dx[] = {-1,0,1,0};
int dy[] = {0,1,0,-1};
struct NODE{
	int x1,y1,x2,y2,d;
	NODE(int a,int b,int c,int D,int e){
		x1 = a , y1 = b , x2 = c , y2 = D , d = e;
	}
};
bool done[52][52][52][52] = {0};
bool data[52][52];
int main(){
	int W,H;
	while(cin >> W >> H , W){
		int a,b,c,d;
		cin >> a >> b >> c >> d;
		rep(i,52)rep(j,52)data[i][j] = true;
		rep(i,H)rep(j,W)cin >> data[i+1][j+1];
		queue<NODE> Q;
		Q.push(NODE(a,b,c,d,0));
		int ans = -1;
		rep(i,52)rep(j,52)rep(k,52)rep(l,52)
			done[i][j][k][l] = 0;
		
		while(Q.size()){
			NODE q = Q.front(); Q.pop();
			if(q.d >= 100) break;
			if(done[q.y1][q.x1][q.y2][q.x2])continue;
			else done[q.y1][q.x1][q.y2][q.x2] = true;
			
			if(q.x1 == q.x2 && q.y1 == q.y2){
				ans = q.d;
				break;
			}
			rep(i,4){
				int A = q.x1 + dx[i] , B = q.y1 + dy[i];
				int C = q.x2 - dx[i] , D = q.y2 - dy[i];
				if(data[B][A])A = q.x1 , B = q.y1;
				if(data[D][C])C = q.x2 , D = q.y2;
				Q.push(NODE(A,B,C,D,q.d+1));
			}
		}
		if(~ans){
			cout << ans << endl;
		}else{
			cout << "NA" << endl;
		}
	}
}

C++: #include<cstdio>
#include<iostream>
#include<string>
#include<map>
#include<queue>
#include<set>

using namespace std;

#define rep(i,n) for(int i=0;i<n;i++)
#define reps(i,n) for(int i=1;i<=n;i++)

class S{
	public:
	int a,b,c,d;
	int val;
	S(int a,int b,int c,int d,int val):
	a(a),b(b),c(c),d(d),val(val){}
};

int ch[55][55][55][55];

int main(){
	while(1){
		int n,m;
		cin>>n>>m;
		if(n==0)break;
		
		int sa,sb,sc,sd;
		cin>>sa>>sb>>sc>>sd;
		
		int masu[55][55];
		rep(i,n){
			rep(j,m){
				cin>>masu[i][j];
			}
		}
		
		rep(i,55)rep(j,55)rep(k,55)rep(p,55)ch[i][j][k][p]=0;
		
		queue<S> que;
		que.push(S(sb,sa,sd,sc,0));
		
		int dx[4]={-1,0,1,0};
		int dy[4]={0,1,0,-1};
		
		int ans=-1;
		while(1){
			if(que.empty())break;
			
			S u = que.front();
			que.pop();
			
			
			if(u.a<=0 || u.b<=0 || u.c<=0 || u.d<=0)continue;
			if(u.a>m || u.c>m || u.b>n || u.d>n)continue;
			
			if(ch[u.a][u.b][u.c][u.d]==1)continue;
			ch[u.a][u.b][u.c][u.d]=1;
			
			
			if(u.a == u.c && u.b==u.d){
				ans = u.val;
				break;
			}
			
			S e = u;
			e.val++;
			rep(i,4){
				e.a += dx[i];
				e.b += dy[i];
				rep(j,4){
					e.c += dx[j];
					e.d += dy[j];
					
					if(masu[e.a][e.b]==1 || masu[e.c][e.d]==1){
					}else if(ch[u.a][u.b][u.c][u.d]==1){
					}else{
						que.push(e);
					}
					
					e.c -= dx[j];
					e.d -= dy[j];
				}
				e.a -= dx[i];
				e.b -= dy[i];
			}
		}
		printf("%d\n",ans);
	}
}

C++: #include<iostream>
#include<utility>
#include<queue>
#include<map>
using namespace std;
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
int main() {
	int W, H, tx, ty, kx, ky;
	bool d[52][52];
	map<pair<pair<int, int>, pair<int, int> >,bool> m;
	pair<pair<int, int>, pair<int, int> >num;
	pair<pair<int, int>, pair<int, int> >copy;
	while (true) {
		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;
			}
		}
		cin >> tx >> ty >> kx >> ky;
		for (int i = 1; i < H + 1; i++) {
			for (int j = 1; j < W + 1; j++) {
				cin >> d[j][i];
			}
		}
		num.first.first = tx;
		num.first.second = ty;
		num.second.first = kx;
		num.second.second = ky;
		queue<pair<pair<int, int>, pair<int, int> > > q;
		q.push(num);
		int qsize = q.size();
		int loopcount = 0;
		while (!q.empty()) {
			num = q.front();
			q.pop();
			if (qsize == 0) {
				qsize = q.size()+1;
				loopcount++;
				if (loopcount == 100) {
					cout << "NA" << endl;
					break;
				}
			}
			qsize--;
			if (num.first.first == num.second.first && num.first.second == num.second.second) {
				cout << loopcount << endl;
				break;
			}
			for (int i = 0; i < 4; i++) {
				if (!d[num.first.first + dx[i]][num.first.second + dy[i]]) {
					copy.first.first = num.first.first + dx[i];
					copy.first.second = num.first.second + dy[i];
				}
				if (!d[num.second.first - dx[i]][num.second.second - dy[i]]) {
					copy.second.first = num.second.first - dx[i];
					copy.second.second = num.second.second - dy[i];
				}
				if (!m[copy]) {
					m[copy] = true;
					q.push(copy);
				}
			}
			if (q.empty()) {
				cout << "NA" << endl;
			}
		}
	}
	return 0;
}