FZU 1560 Binary Bit Benchmark

 

Binary Bit Benchmark

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Time Limit:1s	Memory limit:32M
Accepted Submit:95	Total Submit:197

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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 (binary number). Given a year 1960 <= y <= 2160, what will be the Factstone rating of Amtel's most recently released chip? Input 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. Output For each test case, output a line giving the Factstone rating. Sample Input 1960 1981 0 Sample Output 3 8 Original: FOJ月赛-2007年12月

 

解题：

       要看懂题目。题目要求解n!<2^bit，其中n的最大值。代码中大数相比要运用到对数。

#include <iostream> #include <math.h> using namespace std; int main() { long year,n; long double a,b; a=0;b=1;n=0;a=n; while (cin>>year && year!=0) { year=year/10-196+2; b=pow((double)2,(double)year); while(a<b) { a+=log10((double)++n)/log10((double)2); } cout<<n-1<<endl; } return 0; }