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 <map>
#include <cstdlib>
#include <algorithm>
#include <string>

using namespace std;

int h, w;

char data[30][30];
char next[30][30];
int dy[] = {0, -1, 0, 1};
int dx[] = {1, 0, -1, 0};
map<char, int> ctoi;
string itoc = "ENWS";

void copy(){
   for(int i=0;i<h;++i){
      for(int j=0;j<w;++j){
         data[i][j] = next[i][j];
      }
   }
}

main(){
   ctoi['E'] = 0;
   ctoi['N'] = 1;
   ctoi['W'] = 2;
   ctoi['S'] = 3;
   while(cin >> w >> h && (h || w)){
      int p = 0;
      for(int i=0;i<h;++i){
         for(int j=0;j<w;++j){
            cin >> next[i][j];
            if(next[i][j] == 'E' ||
               next[i][j] == 'N' ||
               next[i][j] == 'W' ||
               next[i][j] == 'S') ++p;
         }
      }
      copy();
      int t;
      for(t=0;t<=180;++t){
         if(p == 0) break;
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '#' ||
                  data[i][j] == '.' ||
                  data[i][j] == 'X') continue;
               for(int k=0;k<4;++k){
                  int d = (ctoi[data[i][j]] + 3 + k) % 4;
                  int ty = i + dy[d];
                  int tx = j + dx[d];
                  if(ty<0 || ty>=h) continue;
                  if(tx<0 || tx>=w) continue;
                  if(data[ty][tx] == '.' || data[ty][tx] == 'X'){
                     data[i][j] = itoc[d];
                     break;
                  }
               }
            }
         }
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '.' || data[i][j] == 'X'){
                  for(int k=0;k<4;++k){
                     int ty = i + dy[k];
                     int tx = j + dx[k];
                     if(ty<0 || ty>=h) continue;
                     if(tx<0 || tx>=w) continue;
                     if(data[ty][tx] == '#' ||
                        data[ty][tx] == '.' ||
                        data[ty][tx] == 'X') continue;
                     if(abs(ctoi[data[ty][tx]] - k) == 2){
                        if(data[i][j] == 'X') --p;
                        else next[i][j] = data[ty][tx];
                        next[ty][tx] = '.';
                        break;
                     }
                  }
               }
            }
         }
         copy();
      }
      if(t > 180) cout << "NA" << endl;
      else cout << t << endl;
   }
   return 0;
}

C++: #include <bits/stdc++.h>
using namespace std;
enum {W, S, E, N};
const int dx[] = {0, 1, 0, -1};
const int dy[] = {-1, 0, 1, 0};
struct P {
	int x, y, ang;
	P(){}
	P(int x, int y, int ang) : x(x), y(y), ang(ang) {}
	bool operator < (const P &t) const {
		return ang < t.ang;
	}
};

int n, m;
bool grid[32][32];
bool pre[32][32];
bool goal[32][32];
vector<P> ps;

void solve()
{
	int res = 0;
	while (ps.size()){
		if (++res > 180){
			puts("NA");
			return;
		}
		
		for (int i = 0; i < ps.size(); i++){
			//printf("%d %d %d\n", i, ps[i].x, ps[i].y);
			
			for (int t = -1; t < 3; t++){
				int dir = (ps[i].ang + t + 4) % 4;
				int nx = ps[i].x + dx[dir];
				int ny = ps[i].y + dy[dir];
				if (!grid[nx][ny]){
					ps[i].ang = dir;
					break;
				}
			}
		}
		sort(ps.begin(), ps.end());
		for (int i = 0; i < ps.size(); i++){
			int nx = ps[i].x + dx[ps[i].ang];
			int ny = ps[i].y + dy[ps[i].ang];
			if (grid[nx][ny]) continue;
			pre[ps[i].x][ps[i].y] = true;
			grid[nx][ny] = true;
			ps[i].x = nx;
			ps[i].y = ny;
			if (goal[nx][ny]){
				ps.erase(ps.begin() + i--);
			}
		}
		for (int i = 1; i <= n; i++){
			for(int j = 1; j <= m; j++){
				if (pre[i][j]) grid[i][j] = false;
				if (goal[i][j]) grid[i][j] = false;
				pre[i][j] = false;
				
				//printf("%c", grid[i][j] ? '#' : ' ');
			}
			//puts("");
		}
	}
	printf("%d\n", res);
}

int main()
{
	while (scanf("%d %d", &m, &n), m){
		memset(grid, true, sizeof(grid));
		memset(goal, false, sizeof(goal));
		memset(pre, false, sizeof(pre));
		ps.clear();
		for (int i = 1; i <= n; i++){
			for (int j = 1; j <= m; j++){
				char c;
				scanf(" %c", &c);
				if (c == '#'){
					grid[i][j] = true;
					continue;
				}
				else if (c == 'X'){
					goal[i][j] = true;
				}
				else if (c == 'W'){
					grid[i][j] = true;
					ps.push_back(P(i, j, W));
				}
				else if (c == 'S'){
					grid[i][j] = true;
					ps.push_back(P(i, j, S));
				}
				else if (c == 'E'){
					grid[i][j] = true;
					ps.push_back(P(i, j, E));
				}
				else if (c == 'N'){
					grid[i][j] = true;
					ps.push_back(P(i, j, N));
				}
				else {
					grid[i][j] = false;
				}
			}
		}
		solve();
	}
}