HDU4850 Wow! Such String! —— 字符串构造

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4850

代码如下：

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <string>
 #include <vector>
 #include <map>
 #include <set>
 #include <queue>
 #include <sstream>
 #include <algorithm>
 using namespace std;
 #define pb push_back
 #define mp make_pair
 #define ms(a, b)  memset((a), (b), sizeof(a))
 #define eps 0.0000001
 typedef long long LL;
 const int INF = 2e9;
 const LL LNF = 9e18;
 const int mod = 1e9+;
 const int maxn = ***;
 int a[maxn+];
 int vis[][][][];

 void solve()
 {
     a[] = a[] = a[] = ;
     for(int i = ; i<maxn+; i++)
     {
         for(int j = ; j>=; j--)
         {
             if(vis[a[i-]][a[i-]][a[i-]][j]==)
             {
                 vis[a[i-]][a[i-]][a[i-]][j] = ;
                 a[i] = j;
                 break;
             }
         }
     }
 }

 int main()
 {
     int n;
     solve();
     while(scanf("%d",&n)!=EOF)
     {
         if(n>maxn+)
             printf("Impossible");
         else
             for(int i = ; i<n; i++)
                 printf("%c",a[i]+'a');
         putchar('\n');
     }
 }