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<algorithm>
#include<vector>
#include<cmath>
#include<cassert>
#include<map>
#include<queue>
#define REP(i,s,n) for(int i=s;i<n;i++)
#define rep(i,n) REP(i,0,n)
#define inf (1<<28)
#define MAX 35
#define next(a,b) ((((a+3)%4)+b)%4)
using namespace std;

struct P
{
  int x,y,dir;
  P(int x=inf,int y=inf,int dir=inf):x(x),y(y),dir(dir){}
};

int dx[] = {+1,+0,-1,+0};
int dy[] = {+0,-1,+0,+1};
int H,W;
char G[MAX][MAX];
int  I[MAX][MAX];
int  D[MAX][MAX];
int  Next[MAX][MAX];
string DIR = "ENWS";
vector<P> vec;

bool Finish()
{
  rep(i,vec.size())
    {
      if(G[vec[i].y][vec[i].x] != 'X')return false;
    }
  return true;
}

void print()
{
  cout << "print- ---" << endl;
  rep(i,H)
    {
      rep(j,W)
	{
	  cout << G[i][j];
	}
      cout << endl;
    }
  cout << endl;
}
void print2()
{
  cout << "2print- ---" << endl;
  rep(i,H)
    {
      rep(j,W)
	{
	  cout << D[i][j];
	}
      cout << endl;
    }
  cout << endl;
}

void decide()
{
  rep(i,vec.size())
    {
      int x = vec[i].x;
      int y = vec[i].y;
      if(G[y][x] == 'X')continue;
      int dir = vec[i].dir;
      rep(j,4)
	{
	  int nx = x + dx[next(dir,j)];
	  int ny = y + dy[next(dir,j)];
	  if(!(0 <= nx && nx < W && 0 <= ny && ny < H))continue;
	  if(!(G[ny][nx] == '.' || G[ny][nx] == 'X'))continue;
	  Next[y][x] = next(dir,j);
	  D[ny][nx]++;
	  break;
	}
    }
}

bool check(int x,int y,int cx,int cy)
{
  rep(i,4)
    {
      int nx = cx + dx[i];
      int ny = cy + dy[i];
      if(!(0 <= nx && nx < W && 0 <= ny && ny < H))continue;
      if(G[ny][nx] == '.' || G[ny][nx] == 'X' || G[ny][nx] == '#')continue;
      return nx == x && ny == y;
    }
  assert(false);
}

void move()
{
  rep(i,vec.size())
    {
      int x = vec[i].x;
      int y = vec[i].y;
      if(G[y][x] == 'X')continue;
      int dir = vec[i].dir;
   
      int nx = x + dx[Next[y][x]];
      int ny = y + dy[Next[y][x]];
      if(!(0 <= nx && nx < W && 0 <= ny && ny < H))continue;
      if(!(G[ny][nx] == '.' || G[ny][nx] == 'X'))continue;
      if(D[ny][nx] == 0)
	{
	  cout << i << " is out: " << x << "," << y << " -> " << nx << "," << ny << endl; 
	  print();
	  print2();
	}
      assert(D[ny][nx]);
      if(D[ny][nx] == 1 || (D[ny][nx] >= 2 && check(x,y,nx,ny)))
	{
	  G[y][x] = '.';
	  vec[i].x = nx, vec[i].y = ny, vec[i].dir = Next[y][x];
	  if(G[ny][nx] != 'X')G[ny][nx] = DIR[Next[y][x]];
	}

    }
  rep(i,H)rep(j,W)D[i][j] = 0;
}

int main()
{
  while(cin >> W >> H,W|H)
    {
      vec.clear();
      rep(i,H)rep(j,W)
	{
	  cin >> G[i][j];
	  I[i][j] = -inf;
	  if(!(G[i][j] == '.' || G[i][j] == '#' || G[i][j] == 'X'))
	    {
	      char c = G[i][j];
	      int dir = (c=='E'?0:(c=='N'?1:(c=='W'?2:(c=='S'?3:-inf))));
	      vec.push_back(P(j,i,dir));

	    }
	}


      if(vec.empty())
	{
	  cout << 0 << endl;
	  continue;
	}

      rep(phase,180)
	{
	  // print();
	  decide();

	  move();

	  if(Finish())
	    {
	      cout << phase+1 << endl;
	      goto Fin;
	    }
	}
      cout << "NA" << endl;
    Fin:;
    }

  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));
		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();
	}
}