Codeforces Round #449 A. Nephren gives a riddle
http://codeforces.com/contest/896/problem/A
第i个字符串嵌套第i-1个字符串
求第n个字符串的第k个字母
dfs
#include<map> #include<cstdio> #include<iostream> using namespace std; typedef long long LL; char s0[77]={" What are you doing at the end of the world? Are you busy? Will you save us?"}; char s1[35]={" What are you doing while sending "}; char s2[32]={" ? Are you busy? Will you send "}; char s3[3]={" ?"}; LL f[54]; void read(LL &x) { x=0; char c=getchar(); while(!isdigit(c)) c=getchar(); while(isdigit(c)) { x=x*10+c-'0'; c=getchar(); } } char dfs(int x,LL y) { if(x<=53 && y>f[x]) return '.'; if(!x) return s0[y]; if(y<=33) return s1[y]; y-=33; if(y==1) return '"'; y--; if(x>53) return dfs(x-1,y); if(y<=f[x-1]) return dfs(x-1,y); y-=f[x-1]; if(y==1) return '"'; y--; if(y<=30) return s2[y]; y-=30; if(y==1) return '"'; y--; if(y<=f[x-1]) return dfs(x-1,y); y-=f[x-1]; if(y==1) return '"'; y--; return '?'; } int main() { f[0]=75; for(int i=1;i<54;++i) f[i]=68+f[i-1]*2; int q; scanf("%d",&q); int n; LL k; while(q--) { scanf("%d",&n); read(k); printf("%c",dfs(n,k)); } }
Nephren is playing a game with little leprechauns.
She gives them an infinite array of strings, f0... ∞.
f0 is "What are you doing at the end of the world? Are you busy? Will you save us?".
She wants to let more people know about it, so she defines fi = "What are you doing while sending "fi - 1"? Are you busy? Will you send "fi - 1"?" for all i ≥ 1.
For example, f1 is
"What are you doing while sending "What are you doing at the end of the world? Are you busy? Will you save us?"? Are you busy? Will you send "What are you doing at the end of the world? Are you busy? Will you save us?"?". Note that the quotes in the very beginning and in the very end are for clarity and are not a part of f1.
It can be seen that the characters in fi are letters, question marks, (possibly) quotation marks and spaces.
Nephren will ask the little leprechauns q times. Each time she will let them find the k-th character of fn. The characters are indexed starting from 1. If fn consists of less than k characters, output '.' (without quotes).
Can you answer her queries?
The first line contains one integer q (1 ≤ q ≤ 10) — the number of Nephren's questions.
Each of the next q lines describes Nephren's question and contains two integers n and k (0 ≤ n ≤ 105, 1 ≤ k ≤ 1018).
One line containing q characters. The i-th character in it should be the answer for the i-th query.
3
1 1
1 2
1 111111111111
Wh.
5
0 69
1 194
1 139
0 47
1 66
abdef
10
4 1825
3 75
3 530
4 1829
4 1651
3 187
4 584
4 255
4 774
2 474
Areyoubusy
For the first two examples, refer to f0 and f1 given in the legend.