CF897C Nephren gives a riddle

思路：

递归。

比赛的时候脑抽了len[]没算够，wa了几次。

实现：

 #include <bits/stdc++.h>
 using namespace std;
 using ll = long long;
 const string s = "What are you doing at the end of the world? Are you busy? Will you save us?";
 const string t = "What are you doing while sending \"";
 const string v = "\"? Are you busy? Will you send \"";
 const ll len_s = s.length();
 const ll len_t = t.length();
 const ll len_v = v.length();
 ll len[];
 char dfs(ll n, ll k)
 {
     if (n == )
     {
         if (k >=  && k <= len_s) return s[k - ];
         else return '.';
     }
     else if (n >= )
     {
         if (k <= len_t) return t[k - ];
         return dfs(n - , k - len_t);
     }
     else
     {
         if (k <= len_t) return t[k - ];
         else if (k > len_t && k <= len_t + len[n - ])
             return dfs(n - , k - len_t);
         else if (k > len_t + len[n - ] && k <= len_t + len[n - ] + len_v)
             return v[k - len_t - len[n - ] - ];
         else if (k > len_t + len[n - ] + len_v && k <= len_t +  * len[n - ] + len_v)
             return dfs(n - , k - len_t - len[n - ] - len_v);
         else if (k == len_t +  * len[n - ] + len_v + )
             return '\"';
         else if (k == len_t +  * len[n - ] + len_v + )
             return '?';
         else return '.';
     }
 }
 int main()
 {
     len[] = (ll)len_s;
     for (int i = ; i <= ; i++)
     {
         len[i] = len[i - ] *  + len_t + len_v + ;
     }
     ll q, n, k;
     cin >> q;
     while (q--)
     {
         cin >> n >> k;
         cout << dfs(n, k);
     }
     return ;
 }