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<bits/stdc++.h>
using namespace std;
#define rep(i,n) for ( int i = 0; i < n; i++ )
#define REP(i, b, e) for ( int i = b; i <= e; i++ )
#define MAX 100
#define LIMIT 180
#define BLOCK '#'
#define SPACE '.'
#define EXIT 'X'
static const string DIR = "ENWS";
static const int di[4] = { 0, -1, 0, 1 };
static const int dj[4] = { 1, 0, -1, 0 };
int H, W;
char G[MAX + 2][MAX + 2];
bool isPerson(char ch) {
	rep(d, 4)if (ch == DIR[d])return true;
	return false;
}
int getDirection(char ch) {
	rep(d, 4)if (ch == DIR[d])return d;
}
int chengeDirection() {
	int nperson = 0;
	REP(i, 1, H)REP(j, 1, W)	{
			if (!isPerson(G[i][j]))continue;
			nperson++;
			int curd = getDirection(G[i][j]);
			int v = curd;
			curd = ((curd == 0) ? 3 : curd - 1);
			for (int r = curd; r < curd + 4; r++) {
				char ch = G[i + di[r % 4]][j + dj[r % 4]];
				if (ch == SPACE || ch == EXIT) {v = r % 4;break;}
			}
			G[i][j] = DIR[v];
	}
	return nperson;
}
void move() {
	int dir[MAX + 2][MAX + 2];
	rep(i, H+2)rep(j, W+2 )	dir[i][j] = -1;
	REP(i, 1, H)REP(j, 1, W)	{
			if (G[i][j] == SPACE || G[i][j] == EXIT) {
				for (int r = 0; r < 4; r++) {
					char target = G[i + di[r]][j + dj[r]];
					if (isPerson(target) && target == DIR[(r + 2) % 4]) {
						dir[i + di[r]][j + dj[r]] = (r + 2) % 4;	break;
					}
				}
			}
	}
	REP(i, 1, H)REP(j, 1, W)	{
			if (!isPerson(G[i][j]) || dir[i][j] == -1)continue;
			int ni, nj;
			ni = i + di[dir[i][j]];
			nj = j + dj[dir[i][j]];
			if (G[ni][nj] == EXIT) {
				G[i][j] = SPACE;
			} else if (G[ni][nj] == SPACE) {
				G[ni][nj] = G[i][j];
				G[i][j] = SPACE;
			}
		}
}
int main() {
	while (1) {
		cin >> W >> H;
		if (H == 0 && W == 0)
			break;
		rep(i,H+2)	rep(j,W+2)G[i][j] = BLOCK;
		REP(i, 1, H)REP(j, 1, W)	cin >> G[i][j];
		int t = 0;
		while (1) {
			if (t > LIMIT)	break;
			if (!chengeDirection())break;
			move();
			t++;
		}
		if (t > LIMIT)
			cout << "NA" << endl;
		else
			cout << t << endl;
	}
	return 0;
}

C++: #include<iostream>
#include<set>
#include<map>
using namespace std;

typedef pair<int,int> P;

int dir(char a){
  if(a=='E')return 0;
  if(a=='N')return 1;
  if(a=='W')return 2;
  if(a=='S')return 3;
  return -1;
}

char inv_dir(int a){
  if(a==0)return 'E';
  if(a==1)return 'N';
  if(a==2)return 'W';
  return 'S';
}

int main(){
  int h,w;
  string grid[30];
  bool use[30][30];
  int dx[] = {1,0,-1,0},dy[] = {0,-1,0,1};

  while(cin >> w >> h && (w||h)){
    for(int i=0;i<h;i++)cin >> grid[i];

    int ans = 0;
    while(ans<=180){
      set<P> s;
      int num = 0;
      for(int i=0;i<h;i++){
	for(int j=0;j<w;j++){
	  int d = dir(grid[i][j]);
	  if(0<=d){
	    num++;
	    for(int k=-1;k<3;k++){
	      int dd = (d+k+4)%4;
	      int sy = i+dy[dd], sx = j+dx[dd];
	      if(sy<0 || sx<0 || h<=sy || w<=sx)continue;
	      if(grid[sy][sx] == '.' || grid[sy][sx] == 'X'){
		grid[i][j] = inv_dir(dd);
		s.insert(P(sy,sx));
		break;
	      }
	    }
	  }
	}
      }
      if(!num)break;
      for(int i=0;i<h;i++)
	for(int j=0;j<w;j++)use[i][j] = false;

      set<P>::iterator ite;
      for(ite=s.begin();ite!=s.end();ite++){
	int i=(*ite).first,j=(*ite).second;
	if(!use[i][j] && (grid[i][j] == '.' || grid[i][j] == 'X')){
	  for(int k=0;k<4;k++){
	    int sy = i+dy[k], sx = j+dx[k];
	    if(sy<0 || sx<0 || h<=sy || w<=sx || use[sy][sx])continue;
	    int d = dir(grid[sy][sx]);
	    if(d<0)continue;
	    int dd = (k+2)%4;
	    if(d==dd){
	      grid[sy][sx] = '.';
	      if(grid[i][j]!='X')grid[i][j] = inv_dir(d);
	      use[sy][sx] = true;
	      break;
	    }
	  }
	}
	use[i][j] = true;
      }
      ans++;
    }
    if(ans>180)cout << "NA\n";
    else cout << ans << endl;
  }
}