C :

#include<stdio.h>
#include<string.h>
int main()
{
	char c[50];
	char str[10000];
	char lost[5000];
	int n,m,i,ii,iii,iiii,go,gogo,left;
	//n个床位,目前正在使用第m个,i是循环变量
	while(gets(str))
	{
		if(str[0]=='0')
			break;
		n=str[0]-48;
		m=0;
		left=0;
		iii=1;
		for(i=1;i<=n;i++)
		{
			c[i]='0';
		}
		for(i=1;i<=50;i++)
		{
			lost[i]='0';
		}
		for(i=2;i<strlen(str);i++)
		{
			go=0;
			for(ii=1;ii<=n;ii++)
			{
				if(c[ii]==str[i])
				{
					c[ii]='0';
					go=1;
					for(iiii=1;iiii<50;iiii++)
					{
						if(lost[iiii]!='0')
						{
							c[ii]=lost[iiii];
							lost[iiii]='0';
						}
					}
					break;
				}
				if(c[ii]=='0')
				{
					c[ii]=str[i];
					go=1;
					break;
				}
			}
			if(go==0)
			{
				gogo=0;
				for(ii=1;ii<50;ii++)
					if(lost[ii]==str[i])
					{
						lost[ii]='0';
						left++;
						gogo=1;
					}
				if(gogo==0);
				{
					lost[iii]=str[i];
					iii++;
				}
			}
		}
		if(left==0)
			printf("All customers tanned successfully.\n");
		else
			printf("%d customer(s) walked away.\n",left);
	}
	return 0;
}

C++ :

#include <iostream>
#include <string.h>
using namespace std;
int bed[30];
int cus[30];
int main(){
    int n, l, ans;
    string list;
    while(cin>>n, n){
        cin>>list;
        ans = 0; l = list.length();
        memset(bed, 0, sizeof(bed));
        memset(cus, 0, sizeof(cus));
        for (int i = 0; i < l; i++){
            int num = list[i] - 'A' + 1;
            if (!cus[num]){
                cus[num] = n + 1;
                for (int j = 1; j <= n; j++) if (!bed[j]){
                    bed[j] = num;
                    cus[num] = j;
                    break;
                }
            }else{
                if (cus[num] > n){
                    ans++;
                    cus[num] = 0;
                }else{
                    bed[cus[num]] = 0;
                    for (int j = 1; j <= 26; j++) if (cus[j] > n){
                        bed[cus[num]] = j;
                        cus[j] = cus[num];
                        break;
                    }
                    cus[num] = 0;
                }
            }
        }
        if (ans) cout<<ans<<" customer(s) walked away."<<endl;
        else cout<<"All customers tanned successfully."<<endl;
    }
    return 0;
}