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 <sstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <climits>
#include <cfloat>
using namespace std;


int main()
{
    int dir[256];
    dir['E'] = 0;
    dir['N'] = 1;
    dir['W'] = 2;
    dir['S'] = 3;

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

    for(;;){
        int w, h;
        cin >> w >> h;
        if(w == 0)
            return 0;

        vector<string> s(h);
        for(int i=0; i<h; ++i)
            cin >> s[i];

        int n = 0;
        vector<int> y, x, d;
        for(int i=0; i<h; ++i){
            for(int j=0; j<w; ++j){
                if('E' <= s[i][j] && s[i][j] <= 'W'){
                    y.push_back(i);
                    x.push_back(j);
                    d.push_back(dir[s[i][j]]);
                    ++ n;
                    s[i][j] = '!';
                }
            }
        }

        int m = n;
        for(int t=1; t<=180; ++t){
            vector<bool> move(n, false);
            for(int i=0; i<n; ++i){
                if(s[y[i]][x[i]] == 'X')
                    continue;
                for(int j=0; j<4; ++j){
                    int d1 = (d[i] + j + 3) % 4;
                    int y1 = y[i] + dy[d1];
                    int x1 = x[i] + dx[d1];
                    if(s[y1][x1] == '.' || s[y1][x1] == 'X'){
                        d[i] = d1;
                        move[i] = true;
                        break;
                    }
                }
            }

            for(int i=0; i<4; ++i){
                for(int j=0; j<n; ++j){
                    if(!move[j] || d[j] != (i+2)%4)
                        continue;
                    int y1 = y[j] + dy[d[j]];
                    int x1 = x[j] + dx[d[j]];
                    if(s[y1][x1] == '.' || s[y1][x1] == 'X'){
                        s[y[j]][x[j]] = '.';
                        if(s[y1][x1] == 'X'){
                            s[y1][x1] = 'Y';
                            -- m;
                        }else{
                            s[y1][x1] = '!';
                        }
                        y[j] = y1;
                        x[j] = x1;
                    }
                }
            }
            for(int i=0; i<n; ++i){
                if(s[y[i]][x[i]] == 'Y')
                    s[y[i]][x[i]] = 'X';
            }

            if(m == 0){
                cout << t << endl;
                break;
            }
        }

        if(m != 0)
            cout << "NA" << endl;
    }
}

C++: #include<cstdio>
#include<cstring>
#include<iostream>
#include<string>

using namespace std;

int w,h,cnt,rest;
int x[1000],y[1001],dir[1001];
char in[51][51];
int fie[51][51];
int fie2[51][51];
int dx[4]={1,0,-1,0};
int dy[4]={0,-1,0,1};
int sw[1000001][4];

int simulation(){
	int turn=0,rest=cnt;
	while(rest>0){
		turn++;
		if(turn>180)return -1;
		for(int i=0;i<cnt;i++){
			if(fie[x[i]][y[i]]==-2)continue;
			int ndir=(dir[i]+3)%4,j;
			for(j=0;j<4;j++){
				int nx=x[i]+dx[ndir],ny=y[i]+dy[ndir];
				if(nx>=0 && nx<w && ny>=0 && ny<h){
					if(fie[nx][ny]==0 || fie[nx][ny]==-1)break;
				}
				ndir=(ndir+1)%4;
			}
			if(j!=4){
				dir[i]=ndir;
			}
		}
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				fie2[j][i]=fie[j][i];
			}
		}
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				if(fie[j][i]==-2 || fie[j][i]>0)continue;
				for(int k=0;k<4;k++){
					int nx=j+dx[k],ny=i+dy[k];
					if(nx>=0 && nx<w && ny>=0 && ny<h){
						if(fie[nx][ny]>0 && dir[fie[nx][ny]-1]==(k+2)%4){
							x[fie[nx][ny]-1]=j;
							y[fie[nx][ny]-1]=i;
							if(fie[j][i]==-1){
								rest--;
								fie2[nx][ny]=0;
							}
							if(fie[j][i]==0)swap(fie2[j][i],fie2[nx][ny]);
							break;
						}
					}
				}
			}
		}
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				fie[j][i]=fie2[j][i];
			}
		}
	}
	return turn;
}

int main(void){
	while(1){
		scanf("%d%d",&w,&h);
		if(w==0 && h==0)break;
		for(int i=0;i<h;i++)scanf("%s",in[i]);
		cnt=0;
		for(int i=0;i<h;i++){
			for(int j=0;j<w;j++){
				if(in[i][j]=='E' || in[i][j]=='N' || in[i][j]=='W' || in[i][j]=='S'){
					x[cnt]=j;
					y[cnt]=i;
					if(in[i][j]=='E')dir[cnt]=0;
					if(in[i][j]=='N')dir[cnt]=1;
					if(in[i][j]=='W')dir[cnt]=2;
					if(in[i][j]=='S')dir[cnt]=3;
					cnt++;
					fie[j][i]=cnt;
				}
				if(in[i][j]=='X')fie[j][i]=-1;
				if(in[i][j]=='#')fie[j][i]=-2;
				if(in[i][j]=='.')fie[j][i]=0;
			}
		}
		int res=simulation();
		if(res==-1)printf("NA\n");
		else printf("%d\n",res);
	}
	return 0;
}