[原创]hdu 2588 GCD [欧拉函数]【数论】*

2016-08-11 11:48:04 Tabris_ 阅读数：345

https://blog.csdn.net/qq_33184171/article/details/52181264

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GCD

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1700 Accepted Submission(s): 829

Problem Description
The greatest common divisor GCD(a,b) of two positive integers a and b,sometimes written (a,b),is the largest divisor common to a and b,For example,(1,2)=1,(12,18)=6.
(a,b) can be easily found by the Euclidean algorithm. Now Carp is considering a little more difficult problem:
Given integers N and M, how many integer X satisfies 1<=X<=N and (X,N)>=M.

Input
The first line of input is an integer T(T<=100) representing the number of test cases. The following T lines each contains two numbers N and M (2<=N<=1000000000, 1<=M<=N), representing a test case.

Output
For each test case,output the answer on a single line.

Sample Input
3
1 1
10 2
10000 72

Sample Output
1
6
260
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$当[d|N]成立,那么就是求\gcd(N,x)=d的个数,\\显然只\gcd(N,d)=d,当且仅当\gcd(N,d*z)=d$

gcd(a,b)>=c 可以转化成gcd(a/c,b/c)=1;

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