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
		}
		if ans<=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<stdio.h>
#define QUEUE_MAX 1000
typedef struct {
    int x;
	int y;
} queue_t;
queue_t t[QUEUE_MAX],k[QUEUE_MAX];
int thead=0,khead=0,tnum=0,knum=0;
int tpush( int vx, int vy ) {
	if(thead+tnum<QUEUE_MAX){
		t[thead+tnum].x=vx;
		t[thead+tnum].y=vy;
		tnum++;
		return 0;
	}
}
int tpop( int *vx, int *vy ) {
	if( tnum > 0 ){
		*vx = t[thead].x;
		*vy = t[thead].y;
		tnum--;
		thead++;
		return 0;
	}
}
int kpush( int vx, int vy ) {
	if(khead+knum<QUEUE_MAX){
		k[khead+knum].x=vx;
		k[khead+knum].y=vy;
		knum++;
		return 0;
	}
}
int kpop( int *vx, int *vy ) {
	if( knum > 0 ){
		*vx = k[khead].x;
		*vy = k[khead].y;
		knum--;
		khead++;
		return 0;
	}
}
int main(){
	while(1){
		int x,y,d[50][50],i,j,tlx[4]={0,1,0,-1},tly[4]={-1,0,1,0},cnt=0,tfx,tfy,kfx,kfy,klx[4]={0,-1,0,1},kly[4]={1,0,-1,0},tc[50][50]={},kc[50][50]={},tm[50][50]={},km[50][50]={},mx,my,f=0,h[50][50]={};
		thead=0;
		khead=0;
		tnum=0;
		knum=0;
		scanf("%d %d",&mx,&my);
			if(mx==0&&my==0){
				break;
			}
		scanf("%d %d",&tfx,&tfy);
		scanf("%d %d",&kfx,&kfy);
		tpush(tfx-1,tfy-1);
		kpush(kfx-1,kfy-1);
		for(i=0;i<my;i++){
			for(j=0;j<mx;j++){
					scanf("%d",&d[i][j]);
			}
		}
		while(1){
			while(1){
				tpop(&tfx,&tfy);
				kpop(&kfx,&kfy);
				if(tfx!=1000&&tfy!=1000&&kfx!=1000&&kfy!=1000){
					break;
				}
			}
			if(tfx==kfx&&tfy==kfy){
				break;
			}
			tm[tfy][tfx]=1;
			km[kfy][kfx]=1;
			for(i=0;i<4;i++){
				if(d[tfy+tly[i]][tfx+tlx[i]]==0&&tm[tfy+tly[i]][tfx+tlx[i]]==0&&(tfx+tlx[i])>=0&&(tfx+tlx[i])<mx&&(tfy+tly[i])>=0&&(tfy+tly[i])<my){
					tpush(tfx+tlx[i],tfy+tly[i]);
					tc[tfy+tly[i]][tfx+tlx[i]]=tc[tfy][tfx]+1;
					h[tfy+tly[i]][tfx+tlx[i]]=1;
				}
				else{
					tpush(1000,1000);
				}
				if(d[kfy+kly[i]][kfx+klx[i]]==0&&km[kfy+kly[i]][kfx+klx[i]]==0&&(kfx+klx[i])>=0&&(kfx+klx[i])<mx&&(kfy+kly[i])>=0&&(kfy+kly[i])<my){
					kpush(kfx+klx[i],kfy+kly[i]);
					kc[kfy+kly[i]][kfx+klx[i]]=kc[kfy][kfx]+1;
					h[kfy+kly[i]][kfx+klx[i]]=1;
				}
				else{
					kpush(1000,1000);
				}
			}
			f=0;
			for(i=0;i<my;i++){
				for(j=0;j<mx;j++){
					if(d[i][j]==0&&h[i][j]==0){
						f=1;
					}
				}
			}
			if(f==0){
				break;
			}
		}
		if(tfx==kfx&&tfy==kfy){
				printf("%d\n",tc[tfy][tfx]);
		}
		else{
			printf("NA\n");
		}
	}
	return 0;
}

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

class State{
public:
  int x1,y1,x2,y2,cost;

  State(int tx1,int ty1,int tx2,int ty2,int tcost){
    x1 = tx1;
    y1 = ty1;
    x2 = tx2;
    y2 = ty2;
    cost = tcost;
  }
};

int w,h;
bool t[52][52];
bool closed[52][52][52][52];

int dx1[] = {-1,1,0,0};
int dx2[] = {1,-1,0,0};
int dy1[] = {0,0,1,-1};
int dy2[] = {0,0,-1,1};

int main(void){
  while(cin>>w>>h && (w||h)){
    int x1,y1,x2,y2;
    cin>>x1>>y1>>x2>>y2;
    x1--; y1--; x2--; y2--;

    for(int i=0;i<h;i++){
      for(int j=0;j<w;j++){
        cin>>t[i][j];
      }
    }

    int ans = -1;
    queue<State> open;

    memset(closed,0,sizeof(closed));
    closed[x1][y1][x2][y2] = true;
    open.push(State(x1,y1,x2,y2,0));

    while(!open.empty()){
      State st = open.front(); open.pop();
      if(st.cost >= 100) break;

      if(st.x1 == st.x2 && st.y1 == st.y2){
        ans = st.cost;
        break;
      }

      for(int i=0;i<4;i++){
        int nx1 = st.x1 + dx1[i];
        int ny1 = st.y1 + dy1[i];
        int nx2 = st.x2 + dx2[i];
        int ny2 = st.y2 + dy2[i];
        State nst = st;
        nst.cost++;

        if(nx1>=0 && nx1<w && ny1>=0 && ny1<h && !t[ny1][nx1]){
          nst.x1 = nx1;
          nst.y1 = ny1;
        }
        if(nx2>=0 && nx2<w && ny2>=0 && ny2<h && !t[ny2][nx2]){
          nst.x2 = nx2;
          nst.y2 = ny2;
        }

        if(!closed[nst.x1][nst.y1][nst.x2][nst.y2]){
          closed[nst.x1][nst.y1][nst.x2][nst.y2] = true;
          open.push(nst);
        }
      }
    }

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

  return 0;
}