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(102)
	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 _, 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 += 1
			if next.Turn <= 100 {
				//heap.Push(&pq, next)
				//pq.Push(next)
				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++: #define _USE_MATH_DEFINES
#define INF 10000000
#include <iostream>
#include <sstream>
#include <cmath>
#include <algorithm>
#include <queue>
#include <stack>
#include <limits>
#include <map>
#include <string>
#include <cstring>
#include <set>
#include <deque>
#include <bitset>
#include <list>

using namespace std;

typedef long long ll;
typedef pair <int,int> P;
typedef pair <P,P> PP;
typedef pair <int,PP> PPP;

static const double eps = 1e-8;

static const int moveTo[][2] = {{1,0},{0,-1},{-1,0},{0,1}};
static const int moveToRev[][2] = {{-1,0},{0,1},{1,0},{0,-1}};

int stage[50][50];
int costTable[50][50][50][50];

int bfs(int tx,int ty,int kx,int ky,int w,int h){
	priority_queue<PPP,vector<PPP>,greater<PPP> > que;
	que.push(PPP(0,PP(P(tx,ty),P(kx,ky))));	
	memset(costTable,0x3,sizeof(costTable));

	int res = INF;
	costTable[tx][ty][kx][ky] = 0;
	while(!que.empty()){
		int cost = que.top().first;
		if(res <= cost || cost >= 100){
			return res;
		}

		int tx = que.top().second.first.first;
		int ty = que.top().second.first.second;
		int kx = que.top().second.second.first;
		int ky = que.top().second.second.second;

		if(tx==kx && ty == ky) res = min(res,cost);

		que.pop();

		for(int i=0;i<4;i++){
			int tdx = tx + moveTo[i][0];
			int tdy = ty + moveTo[i][1];

			if((tdx < 0 || tdx >= w || tdy < 0 || tdy >=h) || stage[tdy][tdx]) {
				tdx = tx;
				tdy = ty;
			}

			int kdx = kx + moveToRev[i][0];
			int kdy = ky + moveToRev[i][1];

			if((kdx < 0 || kdx >= w || kdy < 0 || kdy >=h) || stage[kdy][kdx]) {
				kdx = kx;
				kdy = ky;
			}
			if(costTable[tdx][tdy][kdx][kdy] <= cost + 1) continue;
			costTable[tdx][tdy][kdx][kdy] = cost + 1;
			que.push(PPP(cost+1,PP(P(tdx,tdy),P(kdx,kdy))));
		}
	}

	return res;
}

int main(){

	int w,h;
	while(~scanf("%d %d",&w,&h)){
		if(w == h && h==0) break;
		int tx,ty;
		scanf("%d %d",&tx,&ty);
		int kx,ky;
		scanf("%d %d",&kx,&ky);
		for(int y=0;y<h;y++){
			for(int x=0;x<w;x++){
				scanf("%d",&stage[y][x]);
			}
		}

		int res = bfs(tx-1,ty-1,kx-1,ky-1,w,h);
		if(res >= 100) printf("NA\n");
		else printf("%d\n",res);
	}
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
 
#define rep(i, n) for(int i = 0; i < (n); i++)
#define FOR(i, a, b) for(int i = (a); i < (b); i++)
#define all(v) (v).begin(), (v).end()
#define rev(s) (s).rbegin(), (s).rend()
#define MP make_pair
#define X first
#define Y second
 
using namespace std;
 
typedef long long ll;
typedef pair<int, int> P;

int field[50][50];
int visit[50][50][50][50];

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

int w, h;

bool canmove(int x, int y){
	if(x < 0 || x >= w || y < 0 || y >= h) return false;
	if(field[y][x]) return false;
	return true;
}

int main(){

	while(cin >> w >> h, w|h){
		int tx, ty, kx, ky;
		cin >> tx >> ty >> kx >> ky;
		rep(i, h) rep(j, w) cin >> field[i][j];

		memset(visit, 0, sizeof(visit));

		queue<pair<pair<P, P>, int> > q;
		q.push(MP(MP(MP(tx-1, ty-1), MP(kx-1, ky-1)), 0));

		int ans = -1;
		while(!q.empty()){
			P t, k;
			t = q.front().first.first;
			k = q.front().first.second;
			int time = q.front().second;
			q.pop();

			if(visit[t.X][t.Y][k.X][k.Y]) continue;
			visit[t.X][t.Y][k.X][k.Y] = 1;

			if(time >= 100) break;
			if(t == k){
				ans = time;
				break;
			}

			rep(i, 4){
				int ntx = t.X + dx[i];
				int nty = t.Y + dy[i];
				int nkx = k.X - dx[i];
				int nky = k.Y - dy[i];
				if(!canmove(ntx, nty)) ntx = t.X, nty = t.Y;
				if(!canmove(nkx, nky)) nkx = k.X, nky = k.Y;
				q.push(MP(MP(MP(ntx, nty), MP(nkx, nky)), time+1));
			}
		}

		if(ans == -1) cout << "NA" << endl;
		else cout << ans << endl;
	}


	return 0;
}