As
is known, Ackermann function plays an important role in the sphere of
theoretical computer science. However, in the other hand, the dramatic
fast increasing pace of the function caused the value of Ackermann
function hard to calcuate.
Ackermann function can be defined recursively as follows:
Now
Eddy Gives you two numbers: m and n, your task is to compute the value
of A(m,n) .This is so easy problem,If you slove this problem,you will
receive a prize(Eddy will invite you to hdu restaurant to have supper).
Each line of the input will have two integers, namely m, n, where 0 < m < =3.
Note that when m<3, n can be any integer less than 1000000, while m=3, the value of n is restricted within 24.
Input is terminated by end of file.
For each value of m,n, print out the value of A(m,n).
5
11
解析：推公式。
当m == 0时，A(m,n) = n+1;
当m == 1时，A(m,n) = n+2;
当m == 2时，A(m,n) = 2*n+3;
当m == 3时，A(m,n) = 2n+3-3.(计算2n+3时，可用位运算优化)
1 #include <cstdio>
2
3 int main()
4 {
5 int m,n;
6 while(~scanf("%d%d",&m,&n)){
7 if(m == 0)
8 printf("%d\n",n+1);
9 else if(m == 1)
10 printf("%d\n",n+2);
11 else if(m == 2)
12 printf("%d\n",2*n+3);
13 else
14 printf("%d\n",(1<<(n+3))-3);
15 }
16 return 0;
17 }
