SGU175-Encoding

 

Let phi(W) is the result of encoding for algorithm:
1. If the length of W is 1 then phi(W) is W;
2. Let coded word is W = w1w2...wN and K = N / 2 (rounded down);
3. phi(W) = phi(wNwN-1...wK+1) + phi(wKwK-1...w1).
For example, phi('Ok') = 'kO', phi('abcd') = 'cdab'.
Your task is to find position of letter wq in encoded word phi(W).

Input

Given integers N, q (1 <= N <= 10^9; 1<= q <= N), where N is the length of word W.

Output

Write position of letter wq in encoded word phi(W).

Sample test(s)

Input

 

 

9 4

 

Output

 

 

8

phi(W)经过一下步骤得出来一个字符窜：1. W 如果长度为1 ,则 phi(W) 就是 W;2. 我们假设 W = w1w2…wN 以及 K = N / 2 (向下去整);3. phi(W) = phi(wNwN-1…wK+1) + phi(wKwK-1…w1).
例如, phi(‘Ok’) = ‘kO’, phi(‘abcd’) = ‘cdab’

递归。

 

#include<iostream>#include<string.h>#include<stdio.h>#include<ctype.h>#include<algorithm>#include<stack>#include<queue>#include<set>#include<math.h>#include<vector>#include<map>#include<deque>#include<list>using namespace std;int main(){    int n,q,c=1;    cin>>n>>q;    while(n>1)    {        int k=n/2;        if(q<=k)        {            c+=n-k;            n=k;            q=n-q+1;        }        else        {            q=n-q+1;            n-=k;        }    }    cout<<c<<endl;    return 0;}