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

struct S {
	int tx,ty;
	int kx,ky;
	int 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]);
			}
		}
		queue<S> q;
		bool ok=false;
		S s={tx-1,ty-1,kx-1,ky-1,0};
		q.push(s);
		memset(vst,false,sizeof(vst));
		vst[s.tx][s.ty][s.kx][s.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;
					S ns={ntx,nty,nkx,nky,s.turn+1};
					q.push(ns);
				}
			}
		}
		if(!ok) printf("NA\n");
	}
}

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 >> a >> b, 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();
				cout << o.first << " " << o.second << endl;
				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");
	}
}

C++: #include <bits/stdc++.h>
using namespace std;
#define FOR(i,k,n) for(int i = (k); i < (n); i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(a) begin(a),end(a)
#define MS(m,v) memset(m,v,sizeof(m))
#define D10  fixed<<setprecision(10)
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> P;
typedef long long ll;
const ll INF = 114514810;
const ll MOD = 1000000007;
const double EPS = 1e-8;
const double PI = acos(-1.0);
struct edge
{
	int from, to, cost;
	bool operator < (const edge& e) const { return cost < e.cost; }
	bool operator >(const edge& e) const { return cost > e.cost; }
};
int dx[] = { -1, 0, 0, 1 }; int dy[] = { 0, -1, 1, 0 };
bool valid(int x, int y, int h, int w) { return (x >= 0 && y >= 0 && x < h&&y < w); }
///*************************************************************************************///
///*************************************************************************************///
///*************************************************************************************///

int main()
{
	int x, y;
	while (cin >> x >> y, x)
	{
		int tx, ty, kx, ky;
		cin >> tx >> ty >> kx >> ky;
		tx--, ty--, kx--, ky--;
		int fld[55][55];
		REP(i, y)REP(j, x) cin >> fld[i][j];
		queue<pair<P, int>> que;
		set<P> used;
		P beg = P(tx*y + ty, kx*y + ky);
		que.push(make_pair(beg, 0));
		used.insert(beg);
		bool f = true;
		while (que.size())
		{
			auto tmp = que.front();
			que.pop();
			if (tmp.second >= 100) break;
			if (tmp.first.first == tmp.first.second)
			{
				f = false;
				cout << tmp.second << endl;
				break;
			}
			int tmptx = tmp.first.first / y, tmpty = tmp.first.first % y;
			int tmpkx = tmp.first.second / y, tmpky = tmp.first.second % y;
			REP(i, 4)
			{
				int ntx, nty, nkx, nky;
				ntx = tmptx + dx[i], nty = tmpty + dy[i];
				if (!valid(ntx, nty, x, y) || fld[ntx][nty] == 1)
				{
					ntx = tmptx, nty = tmpty;
				}
				nkx = tmpkx - dx[i], nky = tmpky - dy[i];
				if (!valid(nkx, nky, x, y) || fld[nkx][nky] == 1)
				{
					nkx = tmpkx, nky = tmpky;
				}
				int a = ntx*y + nty;
				int b = nkx*y + nky;
				if (used.find(P(a, b)) == used.end())
				{
					used.insert(P(a, b));
					que.push(make_pair(P(a, b), tmp.second + 1));
				}
			}
		}
		if (f) puts("NA");
	}
		return 0;
}