Go: package main

import (
	"bufio"
	"os"
	"strconv"
	"strings"
	"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

type Point struct {
	x, y int
}

func main() {
	dx := []int{1, 0, -1, 0}
	dy := []int{0, -1, 0, 1}
	maze := make([][]rune, 30)
	for i := range maze {
		maze[i] = make([]rune, 30)
	}
	next := make([][]rune, 30)
	for i := range next {
		next[i] = make([]rune, 30)
	}
	check := make([][]int, 30)
	for i := range check {
		check[i] = make([]int, 30)
	}
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		W, _ := strconv.Atoi(buf[0])
		H, _ := strconv.Atoi(buf[1])
		if W == 0 && H == 0 {
			break
		}
		for i := 0; i < H; i++ {
			scanner.Scan()
			buf_ := scanner.Text()
			for j, v := range buf_ {
				maze[i][j] = v
			}
		}
		man := 0
		for i := 0; i < H; i++ {
			for j := 0; j < H; j++ {
				if maze[i][j] != '.' && maze[i][j] != 'X' && maze[i][j] != '#' {
					switch maze[i][j] {
					case 'E':
						maze[i][j] = 0
						man++
					case 'N':
						maze[i][j] = 1
						man++
					case 'W':
						maze[i][j] = 2
						man++
					case 'S':
						maze[i][j] = 3
						man++
					}
				}
			}
		}
		ans := -1
		for t := 0; t <= 180; t++ {
			if man == 0 {
				ans = t
				break
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					check[i][j] = 0x7FFFFFFF
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					if maze[i][j] > 3 {
						continue
					}
					l := (maze[i][j] + 3) % 4
					for k := 0; k < 4; k++ {
						y := i + dy[l]
						x := j + dx[l]
						if 0 <= y && y < H && 0 <= x && x < W && (maze[y][x] == '.' || maze[y][x] == 'X') {
							maze[i][j] = l
							check[y][x] = min(check[y][x], int((l+2)%4))
							break
						}
						l = (l + 1) % 4
					}
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					next[i][j] = maze[i][j]
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					if maze[i][j] > 3 {
						continue
					}
					y := i + dy[maze[i][j]]
					x := j + dx[maze[i][j]]
					if 0 <= y && y < H && 0 <= x && x < W && check[y][x] == int((maze[i][j]+2)%4) {
						if maze[y][x] == '.' {
							next[y][x] = maze[i][j]
						} else if maze[y][x] == 'X' {
							man--
						}
						next[i][j] = '.'
					}
				}
			}
			for i := 0; i < H; i++ {
				for j := 0; j < W; j++ {
					maze[i][j]=next[i][j]
				}
			}
		}
		if ^ans != 0 {
			fmt.Println(ans)
		} else {
			fmt.Println("NA")
		}
	}
}

func min(a, b int) int {
	if a < b {
		return a
	}
	return b
}

C++: #include<iostream>
#include<string>
#include<algorithm>
#include<set>

char field[30][30];

int input(int h,int w);
char rotate(int x,int y);
int move(int h,int w,int remain);

int main()
{
	while(1)
	{
		int h,w,remain,temp;
		std::cin>>w>>h;
		if(h==0&&w==0)break;
		remain=input(h,w);
		int count;
		
		for(count=0;count<=181&&remain>0;count++)
		{
			for(int y=0;y<h;y++)
			{
				for(int x=0;x<w;x++)
				{
					field[y][x]=rotate(x,y);
				}
			}
			remain=move(h,w,remain);
		}
		if(count>180){std::cout<<"NA"<<std::endl;}
		else{std::cout<<count<<std::endl;}
	}
	return 0;
}

int input(int h,int w)
{
	std::string buf;
	int num=0;
	for(int i=0;i<h;i++)
	{
		std::cin>>buf;
		for(int j=0;j<w;j++)
		{
			field[i][j]=buf[j];
			if(field[i][j]=='N'||field[i][j]=='E'||field[i][j]=='S'||field[i][j]=='W')num++;
		}
	}
	return num;
}

char rotate(int x,int y)
{
	char direction=field[y][x];
	char dir;
	switch(direction)//最初は右を向く
	{
	case 'E':
		dir='W';
		break;
	case 'N':
		dir='S';
		break;
	case 'W':
		dir='E';
		break;
	case 'S':
		dir='N';
		break;
	default:
		return direction;
	}
	for(int i=0;i<=4;i++)
	{
		bool determined=false;
		switch(dir)
		{
		case 'E':
			dir='N';
			if(field[y-1][x]=='.'||field[y-1][x]=='X')
			{
				determined=true;
			}
			break;
		case 'N':
			dir='W';
			if(field[y][x-1]=='.'||field[y][x-1]=='X')
			{
				determined=true;
			}
			break;
		case 'W':
			dir='S';
			if(field[y+1][x]=='.'||field[y+1][x]=='X')
			{
				determined=true;
			}
			break;
		case 'S':
			dir='E';
			if(field[y][x+1]=='.'||field[y][x+1]=='X')
			{
				determined=true;
			}
			break;
		}
		if(determined)break;
	}
	
	return dir;
}

int move(int h,int w,int remain)
{
	std::set<std::pair<int,int> > visited;
	for(int y=0;y<h;y++)
	{
		for(int x=0;x<w;x++)
		{
			if(field[y][x]=='.')
			{
				if(field[y][x+1]=='W'&&visited.find(std::pair<int,int>(x+1,y))==visited.end())
				{
					std::swap(field[y][x],field[y][x+1]);
					visited.insert(std::pair<int,int>(x,y));
				}
				else if(field[y-1][x]=='S'&&visited.find(std::pair<int,int>(x,y-1))==visited.end())
				{
					std::swap(field[y][x],field[y-1][x]);
					visited.insert(std::pair<int,int>(x,y));
				}
				else if(field[y][x-1]=='E'&&visited.find(std::pair<int,int>(x-1,y))==visited.end())
				{
					std::swap(field[y][x],field[y][x-1]);
					visited.insert(std::pair<int,int>(x,y));
				}
				else if(field[y+1][x]=='N'&&visited.find(std::pair<int,int>(x,y+1))==visited.end())
				{
					std::swap(field[y][x],field[y+1][x]);
					visited.insert(std::pair<int,int>(x,y));
				}
			}
			else if(field[y][x]=='X')
			{
				remain--;
				if(field[y][x+1]=='W'&&visited.find(std::pair<int,int>(x+1,y))==visited.end())
				{
					field[y][x+1]='.';
				}
				else if(field[y-1][x]=='S'&&visited.find(std::pair<int,int>(x,y-1))==visited.end())
				{
					field[y-1][x]='.';
				}
				else if(field[y][x-1]=='E'&&visited.find(std::pair<int,int>(x-1,y))==visited.end())
				{
					field[y][x-1]='.';
				}
				else if(field[y+1][x]=='N'&&visited.find(std::pair<int,int>(x,y+1))==visited.end())
				{
					field[y+1][x]='.';
				}
				else
				{
					remain++;
				}
			}
		}
	}
	return remain;
}

C++: #include <iostream>
#include <vector>
#include <algorithm>
#include <complex>

using namespace std;

typedef complex<int> P;

struct human {
	P p;
	int dir;

	human(P p, int dir) : p(p), dir(dir) { }
	human() { this -> p = P(0, 0); this -> dir = 0; }
};

bool cp(human a, human b) {
	return a.dir > b.dir;
}

int abs(int n) {
	return n < 0 ? -n : n;
}

P dir(int n) {
	n %= 4;
	return n == 0 ? P(0, -1) : n == 1 ? P(1, 0) : n == 2 ? P(0, 1) : P(-1, 0);
}

int W, H;
int m[30][30];
int state(P p) {
//	if (p.real() < 0 || p.real() >= W || p.imag() < 0 || p.imag() >= H) cout << "ERROR" << endl;
//	cout << p.real() << " " << p.imag() << endl;
	return m[p.imag()][p.real()];
}

int main() {
	while (cin >> W >> H, W || H) {
		vector<human> v;

		for (int y = 0; y < H; ++y) {
			string str; cin >> str;
			for (int x = 0; x < W; ++x)
				m[y][x] =
					  str[x] == '#' ? 1
					: str[x] == 'X' ? -1
					: str[x] == 'N' ? (v.push_back( human( P(x, y), 0) ), 2)
					: str[x] == 'E' ? (v.push_back( human( P(x, y), 1) ), 2)
					: str[x] == 'S' ? (v.push_back( human( P(x, y), 2) ), 2)
					: str[x] == 'W' ? (v.push_back( human( P(x, y), 3) ), 2)
					: 0
					;
		}

		int t = 0;
		while (v.size() && ++t < 180) {
			// 向き変更
			for (int i = 0; i < v.size(); ++i)
				v[i].dir =
					  state(v[i].p + dir(v[i].dir + 1)) <= 0 ? (v[i].dir + 1) % 4
					: state(v[i].p + dir(v[i].dir))     <= 0 ? v[i].dir
					: state(v[i].p + dir(v[i].dir + 3)) <= 0 ? (v[i].dir + 3) % 4
					: state(v[i].p + dir(v[i].dir + 2)) <= 0 ? (v[i].dir + 2) % 4
					: v[i].dir
					;

			// 向きでソート
			sort( v.begin(), v.end(), cp );

			// 移動
			for (int i = 0; i < v.size(); ++i) {
				int s = state(v[i].p + dir(v[i].dir));
				if (s > 0) continue;

				m[v[i].p.imag()][v[i].p.real()] = 0;
				v[i].p += dir(v[i].dir);

				if (s == 0) m[v[i].p.imag()][v[i].p.real()] = 2;
				else v.erase( v.begin() + i-- );
			}
		}

		if (t >= 180) cout << "NA" << endl;
		else cout << t << endl;
	}
}