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

    }
  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 <cstdio>
#include <vector>
#include <algorithm>
#include <string>
#include <map>
#include <set>
#include <queue>
#include <cstring>

using namespace std;

#define reep(i,f,t) for(int i=f ; i<int(t) ; ++i)
#define rep(i,n) reep(i, 0, n) 

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;

const int dy[] = {0, -1, 0, 1};
const int dx[] = {1, 0, -1, 0};

int main()
{
	int h, w;
	while(scanf("%d%d", &w, &h), w){
		vector<string> field(h);
		rep(i, h){
			char str[32];
			scanf("%s", str);
			field[i] = str;
		}

		int t;
		for(t=0; t<180; ++t){
			int human = 0;
			rep(i, h) rep(j, w){
				int dir = -1;
				if(field[i][j] == 'E') dir = 0;
				if(field[i][j] == 'N') dir = 1;
				if(field[i][j] == 'W') dir = 2;
				if(field[i][j] == 'S') dir = 3;

				if(dir<0)
					continue;
				++human;

				const int dd[] = {3, 0, 1, 2};
				int newdir = dir;
				rep(k, 4){
					int pd = (dir + dd[k]) % 4;
					int py = i + dy[pd];
					int px = j + dx[pd];
					if(field[py][px] == '.' || field[py][px] == 'X'){
						newdir = pd;
						break;
					}
				}
				field[i][j] = "ENWS"[newdir];
			}
			
			vector<string> next = field;
			rep(i, h) rep(j, w){
				rep(k, 4){
					if(field[i][j] != '.' && field[i][j] != 'X')
						continue;
					
					int py = i + dy[k];
					int px = j + dx[k];
					if(py<0 || h<=py || px<0 || w<=px)
						continue;
					
					if(field[py][px] == "WSEN"[k]){
						if(field[i][j] == '.'){
							next[i][j] = field[py][px];
						}else
							--human;
						next[py][px] = '.';
						break;
					}
				}
			}
			if(human == 0)
				break;
			field = next;
			
//			rep(i, h)
//				puts(field[i].c_str());
//			printf("human = %d\n\n", human);
//			getchar();
		}
		if(t == 180)
			puts("NA");
		else
			printf("%d\n", t+1);
	}

	return 0;
}