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 <map>
#include <string>
#include <vector>
using namespace std;

class Maze {
public:
	map<char, char> next;
	map<char, char> prev;
	map<char, pair<int,int>> xy;

	Maze(vector<string> maze) : maze(maze), rest(-1) {
		next = { {'N','E'}, {'E','S'}, {'S','W'}, {'W','N'} };
		prev = { {'E','N'}, {'S','E'}, {'W','S'}, {'N','W'} };
		xy = { {'N', {0, -1}}, {'E', {1, 0}}, {'S', {0, 1}}, {'W', {-1, 0}} };
		H = maze.size();
		W = maze[0].size();
		rest = countPeople();
	}

	void move() {
		changeDirection();
		goAhead();
	}

	int countPeople() {
		if (0 <= rest) return rest;
		int count = 0;
		for (string str : maze) {
			for (char c : str) {
				count += isPerson(c);
			}
		}
		return count;
	}

private:
	vector<string> maze;
	int H, W;
	int rest;

	bool isPerson(char c) {
		return (isalpha(c) && c != 'X');
	}

	bool isPassable(char c) {
		return (c == '.' || c == 'X');
	}

	void changeDirection() {
		for (int i=0; i<H; ++i) {
			for (int j=0; j<W; ++j) {
				if ( ! isPerson(maze[i][j])) continue;
				char dir = next[maze[i][j]];
				for (int k=0; k<4; ++k) {
					int x = j + xy[dir].first;
					int y = i + xy[dir].second;
					if (maze[y][x] == '.' || maze[y][x] == 'X') {
						maze[i][j] = dir;
						break;
					}
					dir = prev[dir];
				}
			}
		}
	}

	void goAhead () {
		for (int i=0; i<H; ++i) {
			for (int j=0; j<W; ++j) {
				if ( ! isPassable(maze[i][j])) continue;
				char dir = 'E';
				for (int k=0; k<4; ++k) {
					int x = j + xy[dir].first;
					int y = i + xy[dir].second;
					if (0 <= x && x < W && 0 <= y && y < H && maze[y][x] == next[next[dir]]) {
						maze[y][x] = '*';
						if (maze[i][j] == '.') {
							maze[i][j] = tolower(next[next[dir]]);
						} else {
							rest --;
						}
						break;
					}
					dir = prev[dir];
				}
			}
		}
		for (int i=0; i<(int)maze.size(); ++i) {
			for (int j=0; j<(int)maze[i].size(); ++j) {
				if (maze[i][j] == '*') {
					maze[i][j] = '.';
				} else {
					maze[i][j] = toupper(maze[i][j]);
				}
			}
		}
	}
};

int main() {
	ios::sync_with_stdio(false);

	int W, H;
	while (cin >> W >> H && (W || H)) {
		vector<string> input(H);
		for (int i=0; i<H; ++i) cin >> input[i];

		Maze maze(input);

		if (maze.countPeople() == 0) {
			cout << 0 << endl;
			continue;
		}

		int second = 0;
		while (0 < maze.countPeople() && second <= 180) {
			maze.move();
			second ++;
		}
		if (second <= 180) cout << second << endl;
		else cout << "NA" << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <map>
#include <cstdlib>
#include <algorithm>
#include <string>

using namespace std;

const int N = 30;

int h, w, t, p;
char data[N][N], next[N][N];
int dy[] = {0, -1, 0, 1};
int dx[] = {1, 0, -1, 0};
map<char, int> ctoi;
string itoc = "ENWS";

void copy(){
   for(int i=0;i<h;++i){
      for(int j=0;j<w;++j){
         data[i][j] = next[i][j];
      }
   }
}

main(){
   ctoi['E'] = 0;
   ctoi['N'] = 1;
   ctoi['W'] = 2;
   ctoi['S'] = 3;
   while(cin >> w >> h && (h || w)){
      p = 0;
      for(int i=0;i<h;++i){
         for(int j=0;j<w;++j){
            cin >> next[i][j];
            if(next[i][j] == 'E' ||
               next[i][j] == 'N' ||
               next[i][j] == 'W' ||
               next[i][j] == 'S') ++p;
         }
      }
      copy();
      for(t=0;t<=181;++t){
         if(p == 0) break;
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '#' ||
                  data[i][j] == '.' ||
                  data[i][j] == 'X') continue;
               for(int k=0;k<4;++k){
                  int d = (ctoi[data[i][j]] + 3 + k) % 4;
                  int ty = i + dy[d];
                  int tx = j + dx[d];
                  if(ty<0 || ty>=h) continue;
                  if(tx<0 || tx>=w) continue;
                  if(data[ty][tx] == '.' || data[ty][tx] == 'X'){
                     data[i][j] = itoc[d];
                     break;
                  }
               }
            }
         }
         for(int i=0;i<h;++i){
            for(int j=0;j<w;++j){
               if(data[i][j] == '.' || data[i][j] == 'X'){
                  for(int k=0;k<4;++k){
                     int ty = i + dy[k];
                     int tx = j + dx[k];
                     if(ty<0 || ty>=h) continue;
                     if(tx<0 || tx>=w) continue;
                     if(data[ty][tx] == '#' ||
                        data[ty][tx] == '.' ||
                        data[ty][tx] == 'X') continue;
                        if(abs(ctoi[data[ty][tx]] - k) == 2){
                        if(data[i][j] == 'X') --p;
                        else next[i][j] = data[ty][tx];
                        next[ty][tx] = '.';
                        break;
                     }
                  }
               }
            }
         }
         copy();
      }
      if(t > 180) cout << "NA" << endl;
      else cout << t << endl;
   }
   return 0;
}