NYOJ 271 The 3n + 1 problem【打表法】

感觉题目有些问题，红字的地方，但是感觉还是输入的数据范围更加准确一点，不然按描述上面的范围，就算打表也会超时的，还有就是这题和hdu 1032一样，令人很不爽的是在杭电 ac的代码拿到nyoj就TLE了，然后看了讨论区，果断加上打表，就过了。哎，实在受不了，至于这么难为我们吗？

The 3n + 1 problem

时间限制： 1000 ms  |  内存限制： 65535 KB

难度： 2

描述

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 before the 1 is printed. 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. 

输入

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 10,000 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.

输出

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).

样例输入

1 10
100 200
201 210
900 1000

样例输出

1 10 20
100 200 125
201 210 89
900 1000 174

来源

POJ

上传者

sadsad

#include<stdio.h>
#define MAXN 10000+10
int arr[MAXN];

int len(int n)
{
	int i=1;
	while(n!=1)
	{
		if(n&1)
			n=3*n+1;
		else
			n/=2;
		++i;
	}
	return i;
}

void count()
{
	int i;
	for(i=1;i!=MAXN;i++)
		arr[i]=len(i);
}


int main()
{
	count();
	int i,t,x,y,maxlen;
	while(~scanf("%d%d",&x,&y))
	{
		maxlen=-1;
		if(x>y)
		{
			t=x;
			x=y;
			y=t;
		}
		for(i=x;i<=y;i++)
		{
			t=arr[i];
			if(t>maxlen)
				maxlen=t;
		}
		printf("%d %d %d\n",x,y,maxlen);
	}
	return 0;
}