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 := &Status{}
		now = pq[0]
		pq = pq[1:]
		if ans <= now.Turn {
			continue
		}
		if _, ok := memo[now.Person]; ok {
			continue
		}
		memo[now.Person] = now.Turn

		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = 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 <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 h, w;
	while (cin >> h >> w, h)
	{
		int tx, ty, kx, ky;
		cin >> tx >> ty >> kx >> ky;
		tx--, ty--, kx--, ky--;
		int fld[50][50];
		REP(i, h)REP(j, w) cin >> fld[i][j];
		queue<pair<P, int>> que;
		set<P> used;
		P beg = P(tx*w + ty, kx*w + 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 / w, tmpty = tmp.first.first % w;
			int tmpkx = tmp.first.second / w, tmpky = tmp.first.second % w;
			REP(i, 4)
			{
				int ntx, nty, nkx, nky;
				ntx = tmptx + dx[i], nty = tmpty + dy[i];
				if (!valid(ntx, nty, h, w) || fld[ntx][nty] == 1)
				{
					ntx = tmptx, nty = tmpty;
				}
				nkx = tmpkx - dx[i], nky = tmpky - dy[i];
				if (!valid(nkx, nky, h, w) || fld[nkx][nky] == 1)
				{
					nkx = tmpkx, nky = tmpky;
				}
				int a = ntx*w + nty;
				int b = nkx*w + 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;
}

C++: #include <iostream>
#include <queue>
#include <map>
using namespace std;

struct state{
    int tx;
    int ty;
    int kx;
    int ky;
    int tim;
};

int main()
{
    while(true){
        int X, Y;
        cin >> X >> Y;
        if(X==0&&Y==0)
            break;

        int d[52][52];
        for(int y=0; y<=Y+1; y++)
            for(int x=0; x<=X+1; x++)
                d[y][x] = 1;

        struct state now;
        cin >> now.tx >> now.ty;
        cin >> now.kx >> now.ky;
        now.tim = 0;

        queue<struct state> que;
        que.push(now);

        map<int, bool> memo;

        for(int y=1; y<=Y; y++)
            for(int x=1; x<=X; x++)
                cin >> d[y][x];

        while(true){
            if(que.empty()){
                cout << "NA" << endl;
                break;
            }

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

            int tk = ((now.tx*100+now.ty)*100+now.kx)*100+now.ky;
            if(memo.find(tk)!=memo.end())
                continue;
            else
                memo[tk] = true;

            if(now.tim>=100){
                cout << "NA" << endl;
                break;
            }

            if(now.tx==now.kx&&now.ty==now.ky){
                cout << now.tim << endl;
                break;
            }

            struct state nxt = now;
            if(d[nxt.ty-1][nxt.tx]==0)
                nxt.ty--;
            if(d[nxt.ky+1][nxt.kx]==0)
                nxt.ky++;
            nxt.tim++;
            que.push(nxt);

            nxt = now;
            if(d[nxt.ty+1][nxt.tx]==0)
                nxt.ty++;
            if(d[nxt.ky-1][nxt.kx]==0)
                nxt.ky--;
            nxt.tim++;
            que.push(nxt);

            nxt = now;
            if(d[nxt.ty][nxt.tx-1]==0)
                nxt.tx--;
            if(d[nxt.ky][nxt.kx+1]==0)
                nxt.kx++;
            nxt.tim++;
            que.push(nxt);

            nxt = now;
            if(d[nxt.ty][nxt.tx+1]==0)
                nxt.tx++;
            if(d[nxt.ky][nxt.kx-1]==0)
                nxt.kx--;
            nxt.tim++;
            que.push(nxt);
        }
    }

    return 0;
}