Language: C++

include<bits/stdc++.h>
using namespace std;
int main(){
  int n,m;
  while(cin>>n>>m,n){
    string s;
    for(int i=0;i<n;i++)s+='#';
    while(m--){
      string p;
      cin>>p;
      if(p=="A"){
        for(int i=0;i<n;i++)
          if(s[i]=='#'){
            s[i]='A';
            break;
          }
      }
      if(p=="B"){
        int pp=0;
        for(int i=n-1;i>=0;i--){
          if(i==n-1){if(s[i-1]!='A'&&s[i]=='#'){pp++,s[i]='B';break;}}
          else if(!i){if(s[i+1]!='A'&&s[i]=='#'){pp++,s[i]='B';break;}}
          else {if(s[i-1]!='A'&&s[i]=='#'&&s[i+1]!='A'){pp++,s[i]='B';break;}}
        }
        if(!pp)for(int i=0;i<n;i++)
             if(s[i]=='#'){
               s[i]='B';
               break;
            }
      }
      if(p=="C"){
        int pp=0;
        for(int i=0;i<n;i++)
          if(s[i]!='#'){
            
            if(i!=n-1){if(s[i+1]=='#'){s[i+1]='C';pp++;break;}}
            if(i){if(s[i-1]=='#'){s[i-1]='C';pp++;break;}}
          }
        if(!pp){
          if(n%2)s[(n+1)/2-1]='C';
          else s[n/2]='C';
        }
      }
      else if(p=="D"){
        int d[n]={},p=0,sp=0;
        for(int i=0;i<n;i++){

          int p1=0,p2=0;
          if(i==n-1)p1=100;
          for(int j=i;j<n;j++)
            if(s[j]=='#')p1++;
            else break;
          for(int j=i;j>=0;j--)
            if(s[j]=='#')p2++;
            else break;
          p1=min(p1,p2);
          p=max(p,p1);
          d[i]=p1;
        }
        for(int i=0;i<n;i++)if(s[i]!='#')sp++;
        if(sp)s[0]='D';
        else for(int i=0;i<n;i++)
          if(d[i]==p){
            s[i]='D';
            break;
          }
      }

    }
    cout<<s<<endl;
  }
}

Compiler output:
a.cc:1:1: error: 'include' does not name a type
    1 | include<bits/stdc++.h>
      | ^~~~~~~
a.cc: In function 'int main()':
a.cc:5:9: error: 'cin' was not declared in this scope
    5 |   while(cin>>n>>m,n){
      |         ^~~
a.cc:6:5: error: 'string' was not declared in this scope
    6 |     string s;
      |     ^~~~~~
a.cc:7:25: error: 's' was not declared in this scope
    7 |     for(int i=0;i<n;i++)s+='#';
      |                         ^
a.cc:9:13: error: expected ';' before 'p'
    9 |       string p;
      |             ^~
      |             ;
a.cc:10:12: error: 'p' was not declared in this scope
   10 |       cin>>p;
      |            ^
a.cc:13:14: error: 's' was not declared in this scope
   13 |           if(s[i]=='#'){
      |              ^
a.cc:21:25: error: 's' was not declared in this scope
   21 |           if(i==n-1){if(s[i-1]!='A'&&s[i]=='#'){pp++,s[i]='B';break;}}
      |                         ^
a.cc:22:26: error: 's' was not declared in this scope
   22 |           else if(!i){if(s[i+1]!='A'&&s[i]=='#'){pp++,s[i]='B';break;}}
      |                          ^
a.cc:23:20: error: 's' was not declared in this scope
   23 |           else {if(s[i-1]!='A'&&s[i]=='#'&&s[i+1]!='A'){pp++,s[i]='B';break;}}
      |                    ^
a.cc:26:17: error: 's' was not declared in this scope
   26 |              if(s[i]=='#'){
      |                 ^
a.cc:34:14: error: 's' was not declared in this scope
   34 |           if(s[i]!='#'){
      |              ^
a.cc:40:18: error: 's' was not declared in this scope
   40 |           if(n%2)s[(n+1)/2-1]='C';
      |                  ^
a.cc:41:16: error: 's' was not declared in this scope
   41 |           else s[n/2]='C';
      |                ^
a.cc:51:16: error: 's' was not declared in this scope
   51 |             if(s[j]=='#')p1++;
      |                ^
a.cc:54:16: error: 's' was not declared in this scope
   54 |             if(s[j]=='#')p2++;
      |                ^
a.cc:56:14: error: 'min' was not declared in this scope; did you mean 'main'?
   56 |           p1=min(p1,p2);
      |              ^~~
      |              main
a.cc:57:13: error: 'max' was not declared in this scope
   57 |           p=max(p,p1);
      |             ^~~
a.cc:60:32: error: 's' was not declared in this scope
   60 |         for(int i=0;i<n;i++)if(s[i]!='#')sp++;
      |                                ^
a.cc:61:15: error: 's' was not declared in this scope; did you mean 'sp'?
   61 |         if(sp)s[0]='D';
      |               ^
      |               sp
a.cc:64:13: error: 's' was not declared in this scope
   64 |             s[i]='D';
      |             ^
a.cc:70:5: error: 'cout' was not declared in this scope
   70 |     cout<<s<<endl;
      |     ^~~~
a.cc:70:11: error: 's' was not declared in this scope
   70 |     cout<<s<<endl;
      |           ^
a.cc:70:14: error: 'endl' was not declared in this scope
   70 |     cout<<s<<endl;
      |              ^~~~