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)
	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)
		if now.Person.Distance() == 0 && ans > now.Turn {
			ans = now.Turn
		}
		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)
			}
		}
	}
	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 <queue>
#include <vector>
#include <cstring>
#include <iostream>
using namespace std;
int H, W, ax, ay, bx, by, x[52][52], dp[52][52][52][52];
int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
int main() {
	while(cin >> W >> H >> ax >> ay >> bx >> by) {
		for(int i = 0; i < H + 2; i++) {
			for(int j = 0; j < W + 2; j++) {
				x[i][j] = 1;
				if(i && i != H + 1 && j && j != W + 1) scanf("%d", &x[i][j]);
			}
		}
		for(int i = 0; i < H + 2; i++) {
			for(int j = 0; j < W + 2; j++) {
				for(int k = 0; k < H + 2; k++) {
					for(int l = 0; l < W + 2; l++) dp[i][j][k][l] = -1;
				}
			}
		}
		dp[ay][ax][by][bx] = 0;
		queue<vector<int> > que; que.push({ax, ay, bx, by});
		bool flag = false;
		while(!que.empty()) {
			vector<int> v1 = que.front(); que.pop();
			for(int i = 0; i < 4; i++) {
				vector<int> v2 = v1;
				if(!x[v1[1] + dy[i]][v1[0] + dx[i]]) v2[0] += dx[i], v2[1] += dy[i];
				if(!x[v1[3] - dy[i]][v1[2] - dx[i]]) v2[2] -= dx[i], v2[3] -= dy[i];
				if(v2[0] == v2[2] && v2[1] == v2[3]) {
					flag = true; break;
				}
				if(dp[v2[1]][v2[0]][v2[3]][v2[2]] == -1) {
					dp[v2[1]][v2[0]][v2[3]][v2[2]] = dp[v1[1]][v1[0]][v1[3]][v1[2]] + 1;
					que.push(v2);
				}
			}
			if(flag) {
				cout << dp[v1[1]][v1[0]][v1[3]][v1[2]] + 1 << endl; break;
			}
		}
		if(!flag) cout << "NA" << endl;
	}
}

C++: #include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<queue>
using namespace std;
typedef struct P{
  int tx,ty,kx,ky,c;
};
int dx[4]={0,1,0,-1};
int dy[4]={-1,0,1,0};
int d[55][55];
bool used[55][55][55][55];
int X,Y;
P fa;
int main(void){
  int ans;
  while(1){

    scanf("%d %d",&X,&Y);
    if(!X && !Y) break;
    scanf("%d %d %d %d",&fa.tx,&fa.ty,&fa.kx,&fa.ky);
    fa.c=0;
    for(int i=1;i<=Y;i++){
      for(int j=1;j<=X;j++){
	scanf("%d",&d[j][i]);
      }
    }


    ans=-1;
    memset(used,0,sizeof(used));
    queue<P> que;
    que.push(fa);

    while(!que.empty()){
      P p=que.front();
      que.pop();
      used[p.tx][p.ty][p.kx][p.ky]=true;
      if(p.c>100)break;
      if(p.tx==p.kx && p.ty==p.ky){
	ans=p.c;
	break;
      }
      if((abs(p.tx-p.kx)+abs(p.ty-p.ky)+1)/2>100-p.c)break;
      for(int i=0;i<4;i++){
	int f=0;
	int x[2]={p.tx,p.kx};
	int y[2]={p.ty,p.ky};
	for(int j=0;j<2;j++){
	  int t=1;
	  if(j)t=-1;
	  if(0<x[j]+dx[i]*t && x[j]+dx[i]*t<=X && 0<y[j]+dy[i]*t && y[j]+dy[i]*t<=Y){
	    if(!d[x[j]+dx[i]*t][y[j]+dy[i]*t]){
	      x[j]+=dx[i]*t;
	      y[j]+=dy[i]*t;
	      f++;
	    }
	  }
	}
	if(!f){
	  continue;
	}
	if(used[x[0]][y[0]][x[1]][y[1]]){
	  continue;
	}
	P pu={x[0],y[0],x[1],y[1],p.c+1};
	used[x[0]][y[0]][x[1]][y[1]]=true;
	que.push(pu);
      }
    }

    if(ans==-1)puts("NA");
    else printf("%d\n",ans);

  }
}