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 <vector>
#include <map>
using namespace std;

const int dx[] = { 1, 0, -1, 0 };
const int dy[] = { 0, 1, 0, -1 };
const int dd[] = { 1, 0, 3, 2 };
const char ch[] = { 'E', 'S', 'W', 'N' };

class Trl {
public:
	int x,y,c,d;
	Trl(int x, int y, int d) : x(x), y(y), d(d) {}
};
typedef pair<int,int> PII;

int main()
{
	int X,Y;
	while (cin >> X >> Y, X||Y)
	{
		string stg[Y];
		for (int i=0; i<Y; i++)
			cin >> stg[i];

		vector<Trl> v;
		for (int y=0; y<Y; y++)
		for (int x=0; x<X; x++)
		{
			if (stg[y][x] == 'E')
				v.push_back(Trl(x,y,0));
			if (stg[y][x] == 'S')
				v.push_back(Trl(x,y,1));
			if (stg[y][x] == 'W')
				v.push_back(Trl(x,y,2));
			if (stg[y][x] == 'N')
				v.push_back(Trl(x,y,3));
		}

		int ans = 0;
		while (v.size() > 0 && ans <= 180)
		{
			int s = v.size();
			vector<Trl> upd;
			vector<int> nx(s,0), ny(s,0);
			for (int i=0; i<s; i++)
			{
				Trl t = v[i];
				bool f=1;
				for (int k=0; k<4; k++)
				{
					nx[i] = t.x + dx[(t.d+dd[k])%4];
					ny[i] = t.y + dy[(t.d+dd[k])%4];
					if (nx[i] < 0 || nx[i] >= X || ny[i] < 0 || ny[i] >= Y) continue;
					if (!(stg[ny[i]][nx[i]] == '.' || stg[ny[i]][nx[i]] == 'X')) continue;
					t.d = (t.d + dd[k]) % 4;
					f=0;
					break;
				}
				if (f) { nx[i] = t.x; ny[i] = t.y; }
				upd.push_back(t);
			}

			vector<int> cx, cy;
			for (int i=0; i<s-1; i++)
			{
				for (int k=i+1; k<s; k++)
				{
					if (nx[i] == nx[k] && ny[i] == ny[k])
					{
						if ((upd[i].d+1)%4 > (upd[k].d+1)%4)
						{
							nx[k] = v[k].x; ny[k] = v[k].y;
						}
						else
						{
							nx[i] = v[i].x; ny[i] = v[i].y;
						}
					}
				}
			}

			int p=0;
			for (int i=0; i<s; i++)
			{
				if (stg[ny[i]][nx[i]] == 'X')
				{
					stg[v[i].y][v[i].x] = '.';
					upd.erase(upd.begin()+p);
				}
				else
				{
					stg[v[i].y][v[i].x] = '.';
					stg[ny[i]][nx[i]] = ch[upd[p].d];
					upd[p].x = nx[i];
					upd[p].y = ny[i];
					p++;
				}
			}
			v = upd;
			ans++;
		}

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

C++: #include <stdio.h>
#include <string.h>
#include <algorithm>
#include <iostream>
#include <math.h>
#include <assert.h>
#include <vector>

using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
static const double EPS = 1e-9;
static const double PI = acos(-1.0);

#define REP(i, n) for (int i = 0; i < (int)(n); i++)
#define FOR(i, s, n) for (int i = (s); i < (int)(n); i++)
#define FOREQ(i, s, n) for (int i = (s); i <= (int)(n); i++)
#define FORIT(it, c) for (__typeof((c).begin())it = (c).begin(); it != (c).end(); it++)
#define MEMSET(v, h) memset((v), h, sizeof(v))

int w, h;
char field[100][100];
int pdir[110][110];
int mapto[300];
int mapfrom[300];
const int dx[4] = { 1, 0, -1, 0 };
const int dy[4] = { 0, -1, 0, 1 };

void PrintField() {
  REP(y, h) {
    printf("%s\n", field[y]);
  }
  puts("");
}

void Push(int nx, int ny, int dir) {
  if (dir == 2) { pdir[ny][nx] = dir; }
  if (pdir[ny][nx] == 2) { return; }
  if (dir == 3) { pdir[ny][nx] = dir; }
  if (pdir[ny][nx] == 3) { return; }
  if (dir == 0) { pdir[ny][nx] = dir; }
  if (pdir[ny][nx] == 0) { return; }
  if (dir == 1) { pdir[ny][nx] = dir; }
  if (pdir[ny][nx] == 1) { return; }
}

int Person() {
  int ret = 0;
  REP(y, h) {
    REP(x, w) {
      if (mapto[(int)field[y][x]] <= 3) { ret++; }
    }
  }
  return ret;
}

int main() {
  MEMSET(mapto, 0x0f);
  mapto[(int)'E'] = 0;
  mapto[(int)'N'] = 1;
  mapto[(int)'W'] = 2;
  mapto[(int)'S'] = 3;
  mapfrom[0] = 'E';
  mapfrom[1] = 'N';
  mapfrom[2] = 'W';
  mapfrom[3] = 'S';
  while (scanf("%d %d", &w, &h), w|h) {
    REP(y, h) {
      scanf("%s", field[y]);
    }
    REP(t, 181) {
      MEMSET(pdir, 0x0f);
      if (Person() == 0) {
        printf("%d\n", t);
        goto next;
      }
      REP(y, h) {
        REP(x, w) {
          int dir = mapto[(int)field[y][x]];
          if (dir <= 3) {
            REP(i, 4) {
              int ndir = (dir + i + 3) % 4;
              int nx = x + dx[ndir];
              int ny = y + dy[ndir];
              if (field[ny][nx] == '.' ||
                  field[ny][nx] == 'X') {
                Push(nx, ny, ndir);
                break;
              }
            }
          }
        }
      }
      REP(y, h) {
        REP(x, w) {
          int dir = pdir[y][x];
          if (dir <= 3) {
            int px = x + dx[(dir + 2) % 4];
            int py = y + dy[(dir + 2) % 4];
            field[py][px] = '.';
            if (field[y][x] == '.') {
              field[y][x] = mapfrom[dir];
            }
          }
        }
      }
    }
    puts("NA");
next:;
  }
}