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 <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;
}

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

				zero.push_back(v[i].p);
				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-- );
			}
			for (int i = 0; i < zero.size(); ++i)
				m[zero[i].imag()][zero[i].real()] = 0;
		}

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

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

#define MAX 40

#define WALL '#'
#define EXIT 'X'
#define TILE '.'

#define EAST 0
#define NORTH 1
#define WEST 2
#define SOUTH 3
#define MAXDIR 4

#define rep(i,b,n) for(int i=(b);i<(n);++i)

int condir[128];
char revdir[4];
const int di[] = {0,-1,0,1};
const int dj[] = {1,0,-1,0};

using namespace std;

typedef pair<int,int> pi;

struct Squares{
  int H,W;
  Squares():H(0),W(0){}
  Squares(int H, int W):H(H),W(W){}
  char D[MAX][MAX];

  bool isEmpty(int i, int j)const{
    return D[i][j] == EXIT || D[i][j] == TILE;
  }
  bool isPerson(int i, int j)const{
    return D[i][j] == 'E' || D[i][j] == 'N' || D[i][j] == 'W' || D[i][j] == 'S';
  }
  void escapersStage1(){
    rep(i,0,H){
      rep(j,0,W){
	if( isPerson(i,j) ){
	  int initk = condir[D[i][j]]-1+MAXDIR;
	  int endk = initk + MAXDIR;
	  for(int k = initk; k < endk; ++k){
	    if( isEmpty( i+di[k%MAXDIR], j+dj[k%MAXDIR] ) ){
	      D[i][j] = revdir[k%MAXDIR];
	      break;
	    }
	  }
	}
      }
    }
  }

  pi getfront(int i, int j, int dir){
    return make_pair(i+di[dir],j+dj[dir]);
  }
  
  void escapersStage2(){
    char newD[MAX][MAX];
    rep(i,0,MAX)rep(j,0,MAX)newD[i][j]=-1;
    rep(i,0,H){
      rep(j,0,W){
	if( isEmpty(i,j) ){
	  for(int k = 0; k < MAXDIR; ++k){
	    pi pfront = getfront(i+di[k],j+dj[k],condir[D[i+di[k]][j+dj[k]]]);
	    if( isPerson( i+di[k], j+dj[k] ) && pfront.first == i && pfront.second == j ){
	      newD[i][j]=D[i+di[k]][j+dj[k]];
	      newD[i+di[k]][j+dj[k]]=TILE;
	      if(D[i][j]==EXIT)newD[i][j]=EXIT;
	      break;
	    }
	  }
	}
      }
    }
    rep(i,0,H)rep(j,0,W){if(newD[i][j]==-1)newD[i][j]=D[i][j];}
    rep(i,0,H)rep(j,0,W){D[i][j]=newD[i][j];}
  }
  int getRemainedPersons(){
    int ret = 0;
    rep(i,0,H)rep(j,0,W){
      if( isPerson(i,j) )++ret;
    }
    return ret;
  }
  void Print(){
    cout << " THE SQUARES COND : " << endl;
    rep(i,0,H){rep(j,0,W){
	cout << D[i][j];}cout<<endl;}
  }
};

int main()
{
  revdir[EAST] = 'E';
  revdir[NORTH] = 'N';
  revdir[WEST] = 'W';
  revdir[SOUTH] = 'S';
  condir[(int)'E'] = EAST;
  condir[(int)'N'] = NORTH;
  condir[(int)'W'] = WEST;
  condir[(int)'S'] = SOUTH;

  while(true){
    int W,H;
    int t = 0;
    cin >> W >> H;

    if( W == 0 && H == 0 ) break;
    
    Squares sq(H,W);
    rep(i,0,H){
      rep(j,0,W){
	cin >> sq.D[i][j];
      }
    }
  
    while( t <= 180 && sq.getRemainedPersons() > 0 ){
      //sq.Print();
      sq.escapersStage1();
      sq.escapersStage2();
      ++t;
    }

    if( t > 180 ) cout << "NA" << endl;
    else cout << t << endl;
  }
  return 0;
}