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 <bits/stdc++.h>
using namespace std;
typedef pair<int,int> P;
typedef pair<P,int> PP;
int dx[4]={0,-1,0,1},dy[4]={1,0,-1,0};
bool check(int n,int m,int x,int y) {return x>=0&&x<n&&y>=0&&y<m;}
int N(char c) {
  if(c=='N') return 0;
  if(c=='W') return 1;
  if(c=='S') return 2;
  return 3;
}

int main() {
  int n,m;
  while(cin >> m >> n && n) {
    string s[n];
    vector<PP> v;
    for(int i=0; i<n; i++) {
      cin >> s[i];
      for(int j=0; j<m; j++) {
        if(isalpha(s[i][j])&&s[i][j]!='X') v.push_back(PP(P(i,j),N(s[i][j])));
      }
    }
    for(int t=0; t<=180; t++) {
      vector<P> d[n][m];
      int c=0;
      for(int i=0; i<v.size(); i++) {
        int nx=v[i].first.first,ny=v[i].first.second,k=v[i].second;
        if(s[nx][ny]=='X') continue;c++;
        for(int j=0; j<4; j++) {
          int kk=(k+j)%4;
          int x=nx+dx[kk],y=ny+dy[kk],f=0;
          if(!check(n,m,x,y)||s[x][y]=='#') continue;
          for(int l=0; l<v.size(); l++) {
            if(s[x][y]!='X'&&v[l].first==P(x,y)) f=1;
          }
          if(f) continue;
          d[x][y].push_back(P((kk+2)%4,i));
          v[i].second=(kk+3)%4;
          break;
        }
      }
      if(!c) {cout << t << endl;goto end;}
      for(int i=0;i<n;i++) {
        for(int j=0;j<m;j++) {
          if(!d[i][j].size()) continue;
          sort(d[i][j].begin(),d[i][j].end());
          P p=d[i][j][0];
          v[p.second]=PP(P(i,j),(p.first+1)%4);
        }
      }
    }
    cout << "NA" << endl;
  end:;
  }
  return 0;
}

C++: #include "bits/stdc++.h"
#include<unordered_map>
#include<unordered_set>
#pragma warning(disable:4996)
using namespace std;
using ld =long double;
const ld eps = 1e-9;

bool check(const vector<vector<pair<int, int>>>&humans, int x, int y) {
	for (int i = 0; i < 4; ++i) {
		auto it=find(humans[i].begin(),humans[i].end(),make_pair(x,y));
		if(it!=humans[i].end())return false;
	}
	return true;
}

int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };

int main()
{
	while (true) {
		int W,H;cin>>W>>H;
		if(!W)break;
		vector<vector<int>>field(H,vector<int>(W));

		string name="WSEN";

		vector<vector<pair<int,int>>>humans(4);
		for (int i = 0; i < H; ++i) {
			string st;cin>>st;
			for (int j = 0; j < W; ++j) {
				char ch(st[j]);
				if(ch=='#')field[i][j]=1;
				else if(ch=='.')field[i][j]=0;
				else if(ch=='X')field[i][j]=2;
				else {
					int k=name.find(ch);
					if (k == string::npos) {
						assert(false);
					}
					else {
						field[i][j]=0;
						k=k%4;
						if(k==0)k=2;
						else if(k==2)k=0;
						humans[k].push_back(make_pair(j,i));
					}
				}
			}
		}

		int time;
		for (time = 1; time < 200; ++time) {
			vector<vector<int>>ways(4);
			vector<vector<pair<int, int>>>next_humans(4);
			for (int i = 0; i < 4; ++i) {
				for (auto human : humans[i]) {
					int now_x = human.first;
					int now_y = human.second;

					int ans = 4;

					for (int plus_way = 1; plus_way > -3; --plus_way) {
						int next_way = (i + 4 + plus_way) % 4;

						int next_x = now_x + dx[next_way];
						int next_y = now_y + dy[next_way];

						if (field[next_y][next_x] != 1 && check(humans, next_x, next_y) == true) {
							ans = next_way;
							break;
						}
					}
					ways[i].push_back(ans);
				}
			}

			vector<vector<int>>moved(H, vector<int>(W));

			vector<int>ts = { 2,1,0,3,4 };
			for (int vv = 0; vv < 5; ++vv) {
				for (int i = 0; i < 4; ++i) {
					for (int j = 0; j < humans[i].size(); ++j) {
						int k = ts[vv];
						if (ways[i][j] == k) {
							if (k == 4) {
								next_humans[ways[i][j]].push_back(humans[i][j]);

							}
							else {
								int next_x = humans[i][j].first + dx[ways[i][j]];
								int next_y = humans[i][j].second + dy[ways[i][j]];

								if (moved[next_y][next_x]) {
									next_humans[ways[i][j]].push_back(humans[i][j]);
								}
								else {

									if (field[next_y][next_x] == 2)continue;
									moved[next_y][next_x] = true;
									next_humans[ways[i][j]].push_back(make_pair(next_x, next_y));
								}
							}

						}
					}

				}
			}
		
			humans=next_humans;
			if (all_of(humans.begin(), humans.end(), [](const vector<pair<int, int>>&v) {return v.empty(); })) {
				break;
			}
		}
		if (time > 180) {
			cout<<"NA"<<endl;
		}
		else {
			cout<<time<<endl;
		}
	}
	return 0;
}