Go: package main

import (
	"bufio"
	"os"
	"strings"
	"strconv"
		"fmt"
)

var scanner = bufio.NewScanner(os.Stdin)

const INF = 0x7FFFFFFF

func main() {
	for scanner.Scan() {
		buf := strings.Split(scanner.Text(), " ")
		n, _ := strconv.Atoi(buf[0])
		m, _ := strconv.Atoi(buf[1])
		if n == 0 && m == 0 {
			break
		}
		chair := make([]string, n+1)
		for i := range chair {
			chair[i] = "#"
		}
		chair[n] = "Sentinel"
		for i := 0; i < m; i++ {
			scanner.Scan()
			switch who := scanner.Text(); who {
			case "A": // 左から眺めて行って空いている席があったら即座に座る
				for j := 0; j < n; j++ {
					if chair[j] == "#" {
						chair[j] = "A"
						break
					}
				}
				// log.Println(chair)
				break // 次の人を読み込む
			case "B":
				flag := true
				// 右端からAの隣でない席を探していく
				for j := n-1; j > -1; j-- {
					if chair[j] == "#" && (j == 0 || chair[j-1] != "A") && chair[j+1] != "A" {
						flag = false
						chair[j] = "B"
						break
					}
				}
				// Aの隣しか空いていないので一番左端の空いている席に座る
				if flag {
					for j := 0; j < n; j++ {
						if chair[j] == "#" {
							chair[j] = "B"
							break
						}
					}
				}
				// log.Println(chair)
				break // 次の人を読み込む
			case "C":
				if i == 0 {
					chair[n/2] = "C" // 先客が誰もいないときは真ん中の椅子に座る
				} else {
					for j := 0; j < n; j++ { // 左から舐めて
						if chair[j] != "#" { // その席が空いていなくて
							if chair[j+1] == "#" { // 右隣が空いているなら座る
								chair[j+1] = "C"
								break
							} else if j != 0 && chair[j-1] == "#" { // 右隣が空いていないので左隣に座る
								chair[j-1] = "C"
								break
							}
						}
					}
				}
				// log.Println(chair)
				break // 次の人を読み込む
			case "D":
				distanceTable := make([]int ,n)
				for j := range distanceTable {
					distanceTable[j] = INF
				}
				for j:= 0; j < n; j++ {
					if chair[j] != "#" {
						for k := 0; k < n; k++ {
							distanceTable[k] = min(distanceTable[k], abs(j-k))
						}
					}
				}
				// log.Println("distanceTAble:", distanceTable)
				at := 0
				distance := 0
				for j := 0; j < n; j++ {
					if distance < distanceTable[j] {
						at = j
						distance = distanceTable[j]
					}
				}
				chair[at] = "D"
				// log.Println(chair)
				break // 次の人を読み込む
			}
		}
		for i := 0; i < n; i++ {
			if i == n-1 {
				fmt.Println(chair[i])
			} else {
				fmt.Printf("%s ", chair[i])
			}
		}
	}
}

func min(a, b int) int {
	if a > b {
		return b
	}
	return a
}

func abs(a int) int {
	if a < 0 {
		return -a
	}
	return a
}

C++: #include<iostream>
using namespace std;
#define rep(i,s,e) for ( int i = s; i <= e; i++ )
#define MAX 10000
char C[MAX+2];
int n, m;

void setLeft(char ch){
    for ( int i = 1; ; i++ ){
	if ( C[i] == '#' ) { C[i] = ch; return; }
    }
}

void setB(){
    for ( int i = n; i >= 1; i-- ){
	if ( C[i] == '#' && C[i-1] != 'A' && C[i+1] != 'A' ){
	    C[i] = 'B'; return;
	}
    }
    setLeft('B');
}

bool isEmpty(){
    rep(i,1,n) if ( C[i] != '#' ) return false;
    return true;
}

void setC(){
    if ( isEmpty() ){ C[n/2+1] = 'C'; return; }
    rep(i,1,n){
	if ( C[i] == '#' ) continue;
	if ( C[i+1] == '#' ) { C[i+1] = 'C'; return; }
	if ( C[i-1] == '#' ) { C[i-1] = 'C'; return; }
    }
}

int getDist( int p ){
    int l = 0, r = 0;
    while( C[p+l-1] == '#' ) l--;
    if ( C[p+l-1] == 'X' ) l = -1000000;
    while( C[p+r+1] == '#' ) r++;
    if ( C[p+r+1] == 'X' ) r = 1000000;
    return min( (-1)*l, r);
}
void setD(){
    if ( isEmpty() ){ C[1] = 'D'; return; }
    int d, mi, md = -1;
    rep(i,1,n){
	if ( C[i] != '#' ) continue;
	d = getDist(i);
	if ( d > md ) {
	    md = d; mi = i;
	}
    }
    C[mi] = 'D';
}

main(){
    char ch;
    while( cin >> n >> m && n && m ){
      assert( n <= 100 );
	rep(i,0,n+1) C[i] = '#';
	C[0] = C[n+1] = 'X';
	rep(i,1,m){ 
	    cin >> ch;
	    if ( ch == 'A' ) setLeft('A');
	    else if ( ch == 'B' ) setB();
	    else if ( ch == 'C' ) setC();
	    else if ( ch == 'D' ) setD();
	}
	rep(i,1,n) cout << C[i];
	cout << endl;
    }
}

C++: #include<iostream>
#include<algorithm>
using namespace std;
int x[1001], n, m; char c;
void _a() {
	for (int i = 1; i <= n; i++) {
		if (x[i] == 0) { x[i] = 1; return; }
	}
}
void _b() {
	for (int i = n; i >= 1; i--) {
		if (x[i] == 0 && x[i - 1] != 1 && x[i + 1] != 1) {
			x[i] = 2; return;
		}
	}
	for (int i = 1; i <= n; i++) {
		if (x[i] == 0) { x[i] = 2; return; }
	}
}
void _c() {
	for (int i = 1; i <= n; i++) {
		if (x[i] >= 1) {
			if (x[i + 1] == 0 && i < n) { x[i + 1] = 3; return; }
			if (x[i - 1] == 0 && i >= 2) { x[i - 1] = 3; return; }
		}
	}
	if (n % 2 == 0) { x[(n / 2) + 1] = 3; }
	else { x[(n + 1) / 2] = 3; }
}
void _d(int p) {
	int dist[1000];
	for (int i = 0; i < 1000; i++) { dist[i] = 10000000; }
	if (p == 0) { x[1] = 4; return; }
	for (int i = 1; i <= n; i++) {
		if (x[i] == 0) { continue; }
		for (int j = 1; j <= n; j++) {
			int D = i - j;
			if (D < 0) { D = -D; }
			dist[j] = min(dist[j], D);
		}
	}
	int maxn = 0, maxid = 0;
	for (int i = 1; i <= n; i++) {
		if (maxn < dist[i]) { maxn = dist[i]; maxid = i; }
	}
	x[maxid] = 4;
}
int main() {
	while (true) {
		cin >> n >> m; if (n == 0 && m == 0) { break; }
		for (int i = 1; i <= 1000; i++) { x[i] = 0; }
		for (int i = 0; i < m; i++) {
			cin >> c;
			int d = c - 'A' + 1;
			if (d == 1) { _a(); }
			if (d == 2) { _b(); }
			if (d == 3) { _c(); }
			if (d == 4) { _d(i); }
		}
		for (int i = 1; i <= n; i++) {
			if (x[i] == 0) { cout << '#'; }
			if (x[i] == 1) { cout << 'A'; }
			if (x[i] == 2) { cout << 'B'; }
			if (x[i] == 3) { cout << 'C'; }
			if (x[i] == 4) { cout << 'D'; }
		}
		cout << endl;
	}
	return 0;
}

C++: #include<iostream>
#include<algorithm>
#include<cstdio>
using namespace std;
#define INF (1 << 29)
int main(){
  char chair[105];
  int n, m;
  char c;
  while(cin >> n >> m, n){
    fill(chair, chair + n, '#');
    chair[n] = 0;
    for(int i = 0;i < m;i++){
      cin >> c;
      switch(c){
      case 'A':
      left :
	for(int j = 0;j < n;j++){
	  if(chair[j] == '#'){
	    chair[j] = c;
	    break;
	  }
	}
	break;
      case 'B':
	for(int j = n - 1;j >= 0;j++){
	  if((j == 0 || chair[j - 1] != 'A') && chair[j] == '#' && chair[j + 1] != 'A'){
	    chair[j] = c;
	    break;
	  }
	  if(j == 0)goto left;
	}
	break;
      case 'C':
	for(int j = 0;j < n;j++){
	  if(j != '#'){
	    if(chair[j + 1] == '#'){
	      chair[j + 1] = c;
	      break;
	    }
	    if(j != 0 && chair[j - 1] == '#'){
	      chair[j - 1] = c;
	      break;
	    }
	  }
	  if(j == n - 1){
	    chair[n / 2] = c;
	  }
	}
	break;
      case 'D':
	int p = 0, s = -1;
	for(int j = 0;j < n;j++){
	  if(chair[j] != '#')continue;
	  int t = INF;
	  for(int k = j;k < n;k++){
	    if(chair[k] != '#'){
	      t = k - j;
	    }
	  }
	  for(int k = j;k >= 0;k--){
	    if(chair[k] != '#'){
	      t = min(t, j - k);
	    }
	  }
	  if(t > s){
	    p = j;
	    s = t;
	  }
	}
	if(p == INF){
	  chair[n - 1] = c;
	}
	else{
	  chair[p] = c;
	}
	break;
      }
    }
    printf("%s\n", chair);
  }
  return 0;
}