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最新推荐文章于 2018-10-11 23:25:20 发布

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最新推荐文章于 2018-10-11 23:25:20 发布

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原文链接：http://www.cnblogs.com/martinue/p/5490571.html

本文探讨了Ackermann函数在理论计算机科学中的重要性及其快速递增特性带来的计算挑战。通过预计算和记忆化搜索的方法，实现了对于特定参数范围内的Ackermann函数值的有效计算，并给出了C++实现代码。

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Problem Description

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).

Input

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.

Output

For each value of m,n, print out the value of A(m,n).

Sample Input

1 3
2 4

Sample Output

5
11

dp记忆化搜索遇到麻烦时需要适当考虑是否是方法选择问题，刚开始用记忆化搜索写的，怎么都栈溢出，百度一下原来这题只能找规律去求解（当编程技巧达到一定程度会忘掉一些最基本的解题方法，当初啥都不会时这种题只能去找规律的，反而学的多了这些基本方法反而容易被丢弃！！）谨以此题警告自己：当一种看似对的方法错了时，得马上想想别的方法转移思路，否则挂死在一棵树上就悲剧了！

#include<iostream>  
using namespace std;  
const int maxn=1001111;  
int dp[4][maxn];  
int x,y;  
void dpstart()  
{  
    memset(dp,0,sizeof(dp));  
    for(int i=0;i<=1000111;i++)  
    {  
        dp[0][i]=i+1;      
    }  
    dp[1][0]=dp[0][1];  
    for(int i=1;i<=1000111;i++)  
    {  
        dp[1][i]=dp[0][dp[1][i-1]];     
    }  
    dp[2][0]=dp[1][1];  
    for(int i=1;i<=1000111;i++)  
    {  
        dp[2][i]=dp[1][dp[2][i-1]];      
    }  
    dp[3][0]=dp[2][1];  
    for(int i=1;i<=24;i++)  
    {  
        dp[3][i]=2*dp[3][i-1]+3;  
    }  
    return ;      
}  
int main()  
{  
    dpstart();  
    while(cin>>x>>y)  
    {  
        cout<<dp[x][y]<<endl;      
    }     
    return 0;  
}

转载于:https://www.cnblogs.com/martinue/p/5490571.html