欧拉工程第64题：Odd period square roots

题目链接

找循环位数是奇数的数有多少个

 

这个自己很难写出来，完全不能暴力

 

维基百科链接 维基百科上面说的很好，上面的算法实现就好了。

就是上面的

 

Java程序：

package project61;

public class P64{
    
    void run(){
        int count = 0;
        int m = 0;
        int d = 1;
        int a0 = 0;
        int a = 0;
        int period = 0;
        for(int S = 2;S<10000;S++){
            period = 0;
            m = 0;
            d = 1;
            a0 = (int) (Math.sqrt(S));
            if(a0*a0 == S) continue;
            a = a0;
            do{
                m = d*a - m;
                d = (S-m*m)/d;
                a = (a0+m)/d;
                period++;
            }while(a!=2*a0);
            if(period%2==1) count++;
        }
        System.out.println(count);
    }
    public static void main(String[] args){
        long  start = System.currentTimeMillis();
        
        new P64().run();
        
        long end = System.currentTimeMillis();
        long time =end - start;
        System.out.println("run time:"+ time/1000+"s"+time%1000+"ms");
    }
}

Python程序

import time as time 

start = time.time()

count  = 0 

for S in range(2,10000):
    m = 0 
    d = 1 
    a0 = int(S**0.5)
    if a0*a0 == S :continue
    preiod = 0 
    a= a0
    while a!=2*a0:
        m = d*a - m
        d = (S - m*m)/d 
        a = int((a0 + m)/d)
        preiod+=1 
    if preiod%2==1:count +=1

end = time.time()  
print "time={0} secs,count={1}".format((end-start),count)

上面两个程序几乎一样的