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 <cstring>

using namespace std;

const int max_size = 30;

void p(char a[max_size][max_size], int sizei, int sizej = 0, int offseti = 0, int offsetj = 0){
	if(!sizej) sizej = sizei;
	for(int i = 0; i < sizei; i++){
		for(int j = 0; j < sizej; j++){
			cout << a[offseti+i][offsetj+j] << ' ';
		}
		cout << endl;
	}
}

char dirchr[] = "ENWS";
int dx[] = {1, 0, -1, 0};
int dy[] = {0, -1, 0, 1};

int dirnum(char d){
	for(int i = 0; i < 4; i++){
		if(dirchr[i] == d) return i;
	}
	//cout << "invalid char" << d << endl;
	//exit(0);
	return -1;
}

void changeDirection(char (*_map)[max_size], int i, int j){
	int startdir = dirnum(_map[i][j]) + 3; // 現在の向きの右から
	for(int k = 0; k < 4; k++){
		int dir = (startdir+k)%4;
		if(_map[i+dy[dir]][j+dx[dir]] == '.' || _map[i+dy[dir]][j+dx[dir]] == 'X'){
			//cout << "(" << i << ", " << j << "): " << _map[i][j] << "->" << dirchr[dir] << endl;
			_map[i][j] = dirchr[dir];
			return;
		}
	}
}

void move(char (*_map)[max_size], int i, int j){
	int dir = dirnum(_map[i][j]);
	char destchar = _map[i+dy[dir]][j+dx[dir]];
	if(destchar == '.'){
		_map[i+dy[dir]][j+dx[dir]] = _map[i][j];
		_map[i][j] = '.';
	}
	if(destchar == 'X'){
		_map[i][j] = '.';
	}
}

void peopleAct(char (*_map)[max_size], int i, int j, void (*func)(char (*)[max_size],int, int), char* filter = "ENWS", int filtersize = 4){
	for(int k = 0; k < filtersize; k++){
		if(_map[i][j] == filter[k]){
			(*func)(_map, i, j);
			break;
		}
	}
}

int main(){
	char square[max_size][max_size];

	int w, h;
	while(cin >> w >> h){
		if(!w && !h) break;
		for(int i = 0; i < h; i++){
			for(int j = 0; j < w; j++){
				cin >> square[i][j];
			}
		}
		int time = 0;
		while(time++ <= 180){
			// 向きを変える処理

			for(int i = 0; i < h; i++){
				for(int j = 0; j < w; j++){
					peopleAct(square, i, j, changeDirection);
					//for(int k = 0; k < 4; k++){
					//	if(square[i][j] == dirchr[k]){
					//		changeDirection(square, i, j);
					//		break;
					//	}
					//}
				}
			}

			// 移動する処理
			// 左、下、右、上の順に処理

			for(int i = 0; i < h; i++){
				for(int j = 0; j < w; j++){ // 左から
					peopleAct(square, i, j, move, "W", 1);
				}
			}

			for(int i = h-1; i >= 0; i--){ // 下から
				for(int j = 0; j < w; j++){
					peopleAct(square, i, j, move, "S", 1);
				}
			}

			for(int i = 0; i < h; i++){
				for(int j = w-1; j >= 0; j-- ){ // 右から
					peopleAct(square, i, j, move, "E", 1);
				}
			}

			for(int i = 0; i < h; i++){ // 上から
				for(int j = 0; j < w; j++){
					peopleAct(square, i, j, move, "N", 1);
				}
			}

			// 人がいなければ避難終了
			for(int i = 0; i < h; i++){
				for(int j = 0; j < w; j++){
					char c = square[i][j];
					if(c != '.' && c != '#' && c != 'X'){
						goto nextloop;
					}
				}
			}
			break;

nextloop: ;
			//p(square, h, w);
			//getchar();
		}

		//p(square, h, w);

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

	return 0;
}

C++: #include <iostream>
#include <string>
#include <vector>
#include <cctype>

using namespace std;

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

int main(){
	while(true){
		int W, H;
		cin >> W >> H;
		if(W == 0 && H == 0){ break; }
		vector<string> field;
		field.push_back(string(W + 2, '#'));
		for(int i = 0; i < H; ++i){
			string line;
			cin >> line;
			field.push_back("#" + line + "#");
		}
		field.push_back(string(W + 2, '#'));
		W += 2; H += 2;
		for(int i = 0; i < H; ++i){
			for(int j = 0; j < W; ++j){
				switch(field[i][j]){
				case 'N': field[i][j] = '0'; break;
				case 'E': field[i][j] = '1'; break;
				case 'S': field[i][j] = '2'; break;
				case 'W': field[i][j] = '3'; break;
				}
			}
		}
		int answer = 0;
		while(answer <= 180){
			bool goal = true;
			for(int i = 0; i < H; ++i){
				for(int j = 0; j < W; ++j){
					if(isdigit(field[i][j])){ goal = false; }
				}
			}
			if(goal){ break; }
			++answer;
			for(int i = 0; i < H; ++i){
				for(int j = 0; j < W; ++j){
					if(!isdigit(field[i][j])){ continue; }
					int next = field[i][j] - '0', offset = 'a';
					for(int k = 5; k >= 0; --k){
						next = (field[i][j] - '0' + k) % 4;
						if(field[i + dy[next]][j + dx[next]] == '.'){ offset = '0'; break; }
						if(field[i + dy[next]][j + dx[next]] == 'X'){ offset = '0'; break; }
					}
					field[i][j] = next + offset;
				}
			}
			for(int i = 0; i < H; ++i){
				for(int j = 0; j < W; ++j){
					int c = field[i][j];
					if(c != '.' && c != 'X'){ continue; }
					for(int k = 5; k > 1; --k){
						int x = j + dx[k % 4], y = i + dy[k % 4];
						if(isdigit(field[y][x])){
							int px = x + dx[field[y][x] - '0'], py = y + dy[field[y][x] - '0'];
							if(px != j || py != i){ continue; }
							field[i][j] = c == 'X' ? '*' : field[y][x] - '0' + 'a';
							field[y][x] = '@';
							break;
						}
					}
				}
			}
			for(int i = 0; i < H; ++i){
				for(int j = 0; j < W; ++j){
					int c = field[i][j];
					if(islower(c)){ field[i][j] = c - 'a' + '0'; }
					if(c == '@'){ field[i][j] = '.'; }
					if(c == '*'){ field[i][j] = 'X'; }
				}
			}
		}
		if(answer > 180){
			cout << "NA" << endl;
		}else{
			cout << answer << endl;
		}
	}
	return 0;
}