hdu 1141

Factstone Benchmark

Time Limit: 10000/5000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 1220    Accepted Submission(s): 706

Problem Description

Amtel has announced that it will release a 128-bit computer chip by 2010, a 256-bit computer by 2020, and so on, continuing its strategy of doubling the word-size every ten years. (Amtel released a 64-bit computer in 2000, a 32-bit computer in 1990, a 16-bit computer in 1980, an 8-bit computer in 1970, and a 4-bit computer, its first, in 1960.)
Amtel will use a new benchmark - the Factstone - to advertise the vastly improved capacity of its new chips. The Factstone rating is defined to be the largest integer n such that n! can be represented as an unsigned integer in a computer word.

Given a year 1960 ≤ y ≤ 2160, what will be the Factstone rating of Amtel's most recently released chip?

There are several test cases. For each test case, there is one line of input containing y. A line containing 0 follows the last test case. For each test case, output a line giving the Factstone rating.

 

Sample Input

  
  

   
   1960
1981
0
  
  

 

Sample Output

  
  

   
   3
8
  
  

 

Source

University of Waterloo Local Contest 2005.09.24

 

Recommend

Eddy

//求n! < 2^m最大的n，其中m为计算机位数。
//两边对数：log(1) + log(2) +...+ log(n) < m* log(2)。
#include <stdio.h>
#include <math.h>
int main()
{
	int t, n, i;
	double r;
	while (~scanf("%d", &t), t)
	{
		n = (t - 1960) / 10 + 2;
		n = 1 << n;
		r = 0;
		i = 1;
		while (r < n)
		{
			r += log(i++) / log(2);
		}
		printf("%d\n", i-2);
	}
	return 0;
}