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<stack>
#include<map>
#include<set>
#include<queue>
#include<cstdio>
#include<climits>
#include<cmath>
#include<cstring>
#include<string>
#include<sstream>

#define f first
#define s second
#define mp make_pair

#define REP(i,n) for(int i=0; i<(int)(n); i++)
#define FOR(i,c) for(__typeof((c).begin()) i=(c).begin(); i!=(c).end(); i++)
#define ALL(c) (c).begin(), (c).end()

using namespace std;

typedef unsigned int uint;
typedef long long ll;

char buff[2][40][40];
int w,h;

int d2i[300];
const char i2d[4] = {'E', 'N', 'W', 'S'};
const int dx[4]   = {1,0,-1,0};
const int dy[4]   = {0,-1,0,1};

#define OK(x,y) (x>=0 && x<w && y>=0 && y<h && (board[y][x] == '.' || board[y][x] == 'X'))

int main(){
  REP(i,300) d2i[i] = -1;
  REP(i,4) d2i[i2d[i]] = i;

  while(scanf("%d%d ",&w,&h),w+h){
    char (*board)[40] = buff[0];
    char (*next)[40]  = buff[1];
    REP(i,h) fgets(board[i],sizeof(board[i]),stdin);
    int t = 0;
    while(++t <= 180){
      int cnt[40][40] = {{0}};
      int rest = 0;

      //ü«ðÏ¦é
      REP(i,h) REP(j,w){
        if(d2i[board[i][j]] != -1){
          int direct = (d2i[board[i][j]] + 3) % 4;
          rest++;
          REP(k,4){
            int x = j + dx[direct];
            int y = i + dy[direct];
            if(OK(x,y)){
              cnt[y][x]++;
              board[i][j] = i2d[direct];
              break;
            }
            direct = (direct + 1) % 4;
          }
        }
      }

      //fobO
      /*
      printf("rest = %d\n",rest);
      REP(i,h){ REP(j,w) printf("%d",cnt[i][j]); puts(""); }
      */

      //{[hÌRs[
      REP(i,h) REP(j,w)
        next[i][j] = (d2i[board[i][j]] == -1 ? board[i][j] : '.');

      bool flag[40][40] = {{false}};
      //ÀÛÉÚ®
      REP(i,h) REP(j,w){
        if(cnt[i][j] > 0){
          REP(k,4){
            int x = j + dx[k];
            int y = i + dy[k];
            if(x < 0 || y < 0) continue;
            if(x >=w || y >=h) continue;
            if(d2i[board[y][x]] != -1 && k == (d2i[board[y][x]] + 2) % 4){
              flag[y][x] = true;
              if(next[i][j] == 'X'){
                rest--;
              }else{
                next[i][j] = board[y][x];
              }
              break;
            }
          }
        }
      }

      //Ú®µÈ©Á½lÌ
      REP(i,h) REP(j,w){
        if(!flag[i][j] && d2i[board[i][j]] != -1){
          next[i][j] = board[i][j];
        }
      }

      //fobO
      //REP(i,h){ REP(j,w) printf("%c",next[i][j]); puts(""); }

      if(rest == 0) break;

      //ÌæÌüêÖ¦
      swap(board, next);
    }
    if(t <= 180) printf("%d\n",t);
    else puts("NA");
  }
  return 0;
}

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() {
	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;
}