HDU-The 3n + 1 problem (3n + 1问题)

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问题及代码：

Problem J The 3n + 1 problem (3n + 1问题)

Time Limit : 2000/1000ms (Java/Other) Memory Limit : 65536/32768K (Java/Other)

Total Submission(s) : 10 Accepted Submission(s) : 4

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Problem Description

Problems in Computer Science are often classified as belonging to a certain class of problems (e.g., NP, Unsolvable, Recursive). In this problem you will be analyzing a property of an algorithm whose classification is not known for all possible inputs.

Consider the following algorithm:

    1.      input n

    2.      print n

    3.      if n = 1 then STOP

    4.           if n is odd then n <- 3n + 1

    5.           else n <- n / 2

    6.      GOTO 2

Given the input 22, the following sequence of numbers will be printed 22 11 34 17 52 26 13 40 20 10 5 16 8 4 2 1

It is conjectured that the algorithm above will terminate (when a 1 is printed) for any integral input value. Despite the simplicity of the algorithm, it is unknown whether this conjecture is true. It has been verified, however, for all integers n such that 0 < n < 1,000,000 (and, in fact, for many more numbers than this.)

Given an input n, it is possible to determine the number of numbers printed (including the 1). For a given n this is called the cycle-length of n. In the example above, the cycle length of 22 is 16.

For any two numbers i and j you are to determine the maximum cycle length over all numbers between i and j.

Input

The input will consist of a series of pairs of integers i and j, one pair of integers per line. All integers will be less than 1,000,000 and greater than 0.

You should process all pairs of integers and for each pair determine the maximum cycle length over all integers between and including i and j.

You can assume that no opperation overflows a 32-bit integer.

Output

For each pair of input integers i and j you should output i, j, and the maximum cycle length for integers between and including i and j. These three numbers should be separated by at least one space with all three numbers on one line and with one line of output for each line of input. The integers i and j must appear in the output in the same order in which they appeared in the input and should be followed by the maximum cycle length (on the same line).

Sample Input

1 10100 200201 210900 1000

Sample Output

1 10 20100 200 125201 210 89900 1000 174

/*    *Copyright (c)2015,烟台大学计算机与控制工程学院    *All rights reserved.    *文件名称：HDU.cpp    *作    者：单昕昕    *完成日期：2015年2月27日    *版 本 号：v1.0        */ #include <iostream>using namespace std;int getnums(int n){    int i=0;    while (n!=1)    {        if(n%2==0)            n/=2;        else            n=3*n+1;        ++i;    }    return i+1;}int main(){    int n1,n2,i;    while (cin>>n1>>n2)    {        int max=0,temp=0,n3=n1,n4=n2;        if(n1>n2)        {            n3=n2;            n4=n1;        }        for(i=n3; i<=n4; ++i)        {            temp=getnums(i);            max=max>temp?max:temp;        }        cout<<n1<<" "<<n2<<" "<<max<<endl;    }    return 0;}

运行结果：

知识点总结：
求两个数之间所有数循环计算的最多次数。

学习心得：

这两周的HDU-OJ让我觉得不仅仅全英文的题目是个硬骨头，而且就算借助了在线翻译工具有的时候题目意思还很难理解。。

革命尚未成功，同志仍需努力啊~~！！！

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