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>
using namespace std;
#define REP(i,b,n) for(int i=b;i<n;i++)
#define rep(i,n)   REP(i,0,n)
#define E 0
#define N 1
#define W 2
#define S 3

int dx[]={1,0,-1,0};
int dy[]={0,-1,0,1};
int opp[]={W,S,E,N};
char m[30][30];

bool move(int r,int c,int y,int x){
  rep(i,4){
    int nex=x+dx[i],ney=y+dy[i];
    if ( nex<0||ney<0||ney>=r||nex>=c)continue;
    if ( m[ney][nex] == opp[i]){
      m[ney][nex]='.';
      if ( m[y][x] == 'X')return true;
      else {m[y][x]=opp[i]+10;return false;}
    }
  }
  return false;
}

void nextD(int r,int c,int y,int x,int d){
  rep(i,4){
    int now = (d+4+i-1)%4;
    int nex=x+dx[now],ney=y+dy[now];
    if ( nex<0||ney<0||nex>=c||ney>=r)continue;
    if ( m[ney][nex]=='.'||m[ney][nex]=='X'){
      m[y][x]=now;
      return;
    }
  }
}


int solve(int r,int c,int person){
  int time=0;
  while(person){
    time++;
    if ( time >180)return -1;
    rep(i,r)
      rep(j,c)
      if ( m[i][j]==E||m[i][j]==S||
	   m[i][j]==W||m[i][j]==N)nextD(r,c,i,j,m[i][j]);

    rep(i,r){
      rep(j,c){
	if ( (m[i][j]=='.'||m[i][j]=='X') && move(r,c,i,j)==true ){
	  person--;
	}
      }
    }

    rep(i,r)
      rep(j,c)if ( m[i][j]>=10 && m[i][j] <=13)m[i][j]-=10;

  }
  if ( person != 0)return -1;
  return time;
}


main(){
  int c,r;
  while(cin>>c>>r && c){
    int cnt = 0;
    rep(i,r){
      cin>>m[i];
      rep(j,c){
	if ( m[i][j]=='E')m[i][j]=E,cnt++;
	else if ( m[i][j] == 'S')m[i][j]=S,cnt++;
	else if ( m[i][j] == 'W')m[i][j]=W,cnt++;
	else if ( m[i][j] == 'N')m[i][j]=N,cnt++;
      }
    }
    int ans = solve(r,c,cnt);
    if ( ans == -1)cout << "NA"<<endl;
    else cout << ans << endl;
  }
  return false;
}

C++: #include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define each(itr,c) for(__typeof(c.begin()) itr=c.begin(); itr!=c.end(); ++itr)
#define all(x) (x).begin(),(x).end()
#define pb push_back
#define fi first
#define se second

struct person
{
    int x,y,dir;
};

// ??? ??? ??? ???
int dx[4]={1,0,-1,0}, dy[4]={0,-1,0,1};
// ??? ??? ??? ???
int dd[4]={3,0,1,2};

inline int detdir(char c)
{
    int r;
    if(c=='E') r=0;
    else if(c=='N') r=1;
    else if(c=='W') r=2;
    else r=3;
    return r;
}

inline char writedir(int d)
{
    string s="ENWS";
    return s[d];
}

int main()
{
    int w,h;
    while(scanf(" %d %d",&w,&h),w)
    {
        vector<string> s(h);
        rep(i,h) cin >>s[i];

        int t=0;
        while(t<181)
        {
            ++t;

            int ct[50][50]={0};

            vector<person> p;
            // ???????????????????±????
            rep(i,h)rep(j,w)
            {
                if(s[i][j]!='.' && s[i][j]!='#' && s[i][j]!='X')
                {
                    int dir=detdir(s[i][j]);
                    rep(k,4)
                    {
                        int ndir=(dir+dd[k])%4;
                        // printf("ndir= %d\n", ndir);
                        int nx=j+dx[ndir], ny=i+dy[ndir];
                        if(s[ny][nx]=='.' || s[ny][nx]=='X')
                        {
                            ++ct[ny][nx];
                            dir=ndir;
                            break;
                        }
                    }

                    s[i][j]=writedir(dir);
                    p.pb(person{j,i,dir});
                }
            }

            for(const auto &a:p)
            {
                int nx=a.x+dx[a.dir], ny=a.y+dy[a.dir];
                if(s[ny][nx]=='.' || s[ny][nx]=='X')
                {
                    if(ct[ny][nx]==1)
                    {
                        if(s[ny][nx]=='.') s[ny][nx]=s[a.y][a.x];
                        s[a.y][a.x]='.';
                    }
                    else
                    {
                        bool found=false;
                        rep(k,4)
                        {
                            int X=nx+dx[k], Y=ny+dy[k];
                            if(X==a.x && Y==a.y) break;

                            if(s[Y][X]=='E' || s[Y][X]=='N' || s[Y][X]=='W' || s[Y][X]=='S') found=true;
                        }

                        if(!found)
                        {
                            if(s[ny][nx]=='.') s[ny][nx]=s[a.y][a.x];
                            s[a.y][a.x]='.';
                        }
                    }
                }
            }

            // printf(" ---time %d ---\n", t);
            // rep(i,h) cout << s[i] <<endl;

            bool done=true;
            rep(i,h)rep(j,w)
            {
                if(s[i][j]=='E' ||s[i][j]=='N' ||s[i][j]=='W' ||s[i][j]=='S') done=false;
            }
            if(done) break;
        }

        if(t==181) printf("NA\n");
        else printf("%d\n",t);
    }
    return 0;
}