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(101)
	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 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)
				pq = append(pq, 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>
#include <set>
#include <list>

using namespace std;

typedef struct {
	int tx, ty;
	int kx, ky;
	int depth;
} DATA;

set<unsigned int> hash;
list<DATA> width_sarch;
int map[100 + 2][100 + 2];

unsigned int calc_hash(DATA &data)
{
	return (data.tx | (data.ty << 8) | (data.kx << 16) | (data.ky << 24));
}

int main(void)
{
	int width, hight;
	int tx, ty, kx, ky;
	DATA add;
	
	while (1){
		hash.clear();
		width_sarch.clear();
		
		scanf("%d%d", &width, &hight);
		if (width == 0 && hight == 0){
			break;
		}
		scanf("%d%d%d%d", &add.tx, &add.ty, &add.kx, &add.ky);
		
		add.depth = 0;
		hash.insert(calc_hash(add));
		width_sarch.push_back(add);
		
		for (int i = 0; i <= hight + 1; i++){
			for (int j = 0; j <= width + 1; j++){
				map[i][j] = 1;
			}
		}
		
		for (int y = 1; y <= hight; y++){
			for (int x = 1; x <= width; x++){
				scanf("%d", &map[x][y]);
			}
		}
		
		while (!width_sarch.empty() && width_sarch.front().depth < 100){
			if (width_sarch.front().tx == width_sarch.front().kx && width_sarch.front().ty == width_sarch.front().ky){
				break;
			}
			
			
			tx = width_sarch.front().tx;
			ty = width_sarch.front().ty;
			kx = width_sarch.front().kx;
			ky = width_sarch.front().ky;
			add.depth = width_sarch.front().depth + 1;
			
			add.ty = ty;
			add.ky = ky;
			
			add.tx = map[tx + 1][ty] == 0 ? tx + 1 : tx;
			add.kx = map[kx - 1][ky] == 0 ? kx - 1 : kx;
			if (hash.find(calc_hash(add)) == hash.end()){
				hash.insert(calc_hash(add));
				width_sarch.push_back(add);
			}
			add.tx = map[tx - 1][ty] == 0 ? tx - 1 : tx;
			add.kx = map[kx + 1][ky] == 0 ? kx + 1 : kx;
			if (hash.find(calc_hash(add)) == hash.end()){
				hash.insert(calc_hash(add));
				width_sarch.push_back(add);
			}
			
			add.tx = tx;
			add.kx = kx;
			
			add.ty = map[tx][ty + 1] == 0 ? ty + 1 : ty;
			add.ky = map[kx][ky - 1] == 0 ? ky - 1 : ky;
			if (hash.find(calc_hash(add)) == hash.end()){
				hash.insert(calc_hash(add));
				width_sarch.push_back(add);
			}
			add.ty = map[tx][ty - 1] == 0 ? ty - 1 : ty;
			add.ky = map[kx][ky + 1] == 0 ? ky + 1 : ky;
			if (hash.find(calc_hash(add)) == hash.end()){
				hash.insert(calc_hash(add));
				width_sarch.push_back(add);
			}
			
			
			width_sarch.pop_front();
		}
		
		if (width_sarch.empty() || width_sarch.front().depth >= 100){
			puts("NA");
		}
		else {
			printf("%d\n", width_sarch.front().depth);
		}
	}
	
	return (0);
}

C++: #include<iostream>
#include<queue>
using namespace std;
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
int main() {
	int W, H, tx, ty, kx, ky;
	int d[52][52];
	bool memo[52][52][52][52];
	while (true) {
		cin >> W >> H;
		if (W == 0)break;
		for (int i = 0; i < W+2; i++) {
			for (int j = 0; j < H+2; j++) {
				for (int k = 0; k < W+2; k++) {
					for (int l = 0; l < H+2; l++) {
						memo[i][j][k][l] = false;
					}
				}
			}
		}
		for (int i = 0; i < W+2; i++) {
			for (int j = 0; j < H+2; j++) {
				d[i][j] = 1;
			}
		}
		cin >> tx >> ty >> kx >> ky;
		for (int i = 1; i < H + 1; i++) {
			for (int j = 1; j < W + 1; j++) {
				cin >> d[i][j];
			}
		}
		pair<pair<int, int>, pair<int, int> >num;
		num.first.first = tx;
		num.first.second = ty;
		num.second.first = kx;
		num.second.second = ky;
		queue<pair<pair<int, int>, pair<int, int> > > q;
		q.push(num);
		int qsize = 1;
		int loopcount = 0;
		while (!q.empty()) {
			num = q.front();
			q.pop();
			if (memo[num.first.first][num.first.second][num.second.first][num.second.second]) {
				continue;
			}
			else {
				memo[num.first.first][num.first.second][num.second.first][num.second.second] = true;
			}
			if (d[num.first.first][num.first.second]
				|| d[num.second.first][num.second.second]) {
				continue;
			}
			if (qsize == 0) {
				qsize = q.size();
				loopcount++;
				if (loopcount == 100) {
					cout << "NA" << endl;
					break;
				}
			}
			qsize--;
			if (num.first.first == num.second.first
				&& num.first.second == num.second.second) {
				cout << loopcount << endl;
				break;
			}
			for (int i = 0; i < 4; i++) {
				pair<pair<int, int>, pair<int, int> >copy;
				copy = num;
				copy.first.first += dx[i];
				copy.first.second += dy[i];
				copy.second.first -=dx[i];
				copy.second.second -= dy[i];
				q.push(copy);
			}
		}
	}
	return 0;
}