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 <vector>
#include <algorithm>
#include <queue>
#include <deque>
#include <string>
#include <cmath>
#include <cstdio>
#define FOR(I,A,B) for(int I =(A);I<(B);++I)
#define FORE(I,B) for(int I =1;I<=(B);++I)
#define REP(I,A) FOR(I,0,A)
const int dx[]={1,0,-1,0},dy[]={0,-1,0,1};
const char dc[]={'E','N','W','S'};
const char dcc[]={'e','n','w','s'};
using namespace std;

int main() {
	// your code goes here
	int W,H;
	while (cin >> W >> H && W){
	char tmp;
	char maps[32][32]={};
	FORE(i,H)
		FORE(j,W)
			cin >> maps[i][j];
	bool ans;
	int next=0;
	while(true){
		ans=false;
		FORE(jj,W){
			int j=W-jj;
			FORE(i,H){
				REP(k,4)
					if(maps[i][j]==dc[k]){
						REP(l,4){
							int n=(k+l+3)%4;
							if(maps[i+dy[n]][j+dx[n]]=='.'){
								maps[i][j]='x';
								maps[i+dy[n]][j+dx[n]]=dcc[n];
							}
							else if(maps[i+dy[n]][j+dx[n]]=='n' && dc[n]=='E'){
								maps[i][j]='x';
								maps[i+dy[n]][j+dx[n]]=dcc[n];
								maps[i+1][j+1]='N';
							}
							else if(maps[i+dy[n]][j+dx[n]]=='X')
								maps[i][j]='x';
							else{
							REP(g,4)
								if(maps[i+dy[n]][j+dx[n]]==dcc[g]){
									maps[i][j]=dc[n];
									goto label;
								}
								continue;
							}
							label:
							break;
						}
					ans=true;
					}
			}
		}
		FORE(i,H){
			FORE(j,W){
				if(maps[i][j]=='x')
					maps[i][j]='.';
				REP(k,4)
					if(maps[i][j]==dcc[k])
						maps[i][j]=dc[k];
			//	cout << maps[i][j];
			}
	//	cout << endl;
		}
		if(!ans || next>180)
			break;
		next++;
	}
	if(next>180)
	cout << "NA" << endl;
	else 
	cout << next << endl;
	}
	return 0;
}

C++: #include<iostream>
#include<vector>
using namespace std;

const string Direction = {"ENWS"};
const int Next[4][2] = {{0, 1}, {-1, 0}, {0, -1}, {1, 0}};
enum {Y, X};

int main() {
    int w, h;
    while(cin >> w >> h, w | h) {
        int time;
        vector<string> field(h);
        for(int i = 0; i < h; ++i) cin >> field[i];

        for(time = 0; time <= 180; ++time) {
//             cout << time << endl;
//             for(auto& s: field)cout<<s<<endl;
            bool ok = true;
            for(const auto& line: field) for(const auto& c: line)
                if(Direction.find(c) != string::npos) ok = false;
            if(ok) break;
            // turn
            for(int i = 0; i < h; ++i) for(int j = 0; j < w; ++j) {
                int index = Direction.find(field[i][j]);
                if(index == string::npos) continue;
                for(int k = 0; k < 4; ++k) {
                    int d = (index + 3 + k) % 4;
                    int y = i + Next[d][Y];
                    int x = j + Next[d][X];
                    if(field[y][x] != '.' && field[y][x] != 'X') continue;
                    field[i][j] = Direction[d];
                    break;
                }
            }
            // move
            vector<vector<int>> used(h, vector<int>(w, 0));
            for(int i = 0; i < h; ++i) for(int j = 0; j < w; ++j) {
                if(field[i][j] != '.' && field[i][j] != 'X') continue;
                if(used[i][j]) continue;
                for(int d = 0; d < 4; ++d) {
                    int y = i + Next[d][Y];
                    int x = j + Next[d][X];
                    if(y < 0 || h <= y) continue;
                    if(x < 0 || w <= x) continue;
                    if(field[y][x] != Direction[(d + 2) % 4]) continue;
                    if(used[y][x]) continue;
                    used[i][j] = 1;
                    used[y][x] = 1;
                    if(field[i][j] == '.') field[i][j] = field[y][x];
                    field[y][x] = '.';
                    break;
                }
            }
        }

        if(time > 180) cout << "NA" << endl;
        else cout << time << endl;
    }
}