The fourth question of "NOIP2007" · Hanoi Twin Towers problem

Title Description Description

Given a, B, c three long enough of the fine column, on the A column is placed 2n holes in the middle of the disk, a total of n different dimensions, each size has two identical discs, note that the two discs are not differentiated (for n=3 case). These discs are now moved to the C-pillar and can be staged on the B-pillar during movement. Requirements:

(1) Only one disc can be moved at a time;

(2) A, B, c three thin column on the disk should be kept small under the large order;

Task: Set an to 2N discs to complete the minimum number of moves required for the above tasks, and for input n, output An.

Enter a description Input Description

is a positive integer n, which indicates that there are 2n discs placed on a column.

Output description Output Description

A single row that contains a positive integer that is the minimum number of moves required to complete the above task.

Sample input Sample Input

2

Sample output Sample Output

6

Data range and Tips Data Size & Hint

For 50% of data, 1<=n<=25

For 100% of data, 1<=n<=200

Try to establish a recursive relationship between an and an-1.

Code:
var  a:array[1..200]of Longint;  B:array[1..10000]of integer;  N,i,j,m:longint;begin  readln (n);  a[1]:=2;  If N<26 then the begin for  i:=2 and n do a[i]:=a[i-1]*2+2;  Writeln (A[n]);  End  Else begin    b[1]:=2;b[2]:=6;b[3]:=8;b[4]:=8;b[5]:=0;b[6]:=1;b[7]:=7;b[8]:=6;    m:=8;    For i:=26 to n does begin for      j:=1 to M do b[j]:=b[j]*2;      b[1]:=b[1]+2;      For J:=1 to M do begin        B[j+1]:=b[j]div 10+b[j+1];        B[J]:=B[J] MoD ten;      End;      Inc (M);    End;    While b[m]=0 do m:=m-1;    For i:=m Downto 1 do write (B[i]);  End;end

The fourth question of "NOIP2007" · Hanoi Twin Towers problem