2013
11-10

# Perfect Pth Powers

We say that x is a perfect square if, for some integer b, x = b2. Similarly, x is a perfect cube if, for some integer b, x = b3. More generally, x is a perfect pth power if, for some integer b, x = bp. Given an integer x you are to determine the largest p such that x is a perfect pth power.

Each test case is given by a line of input containing x. The value of x will have magnitude at least 2 and be within the range of a (32-bit) int in C, C++, and Java. A line containing 0 follows the last test case.

For each test case, output a line giving the largest integer p such that x is a perfect pth power.

17
1073741824
25
0


1
30
2


//* @author: Yeming Hu"cslittleye@gmail.com"
import java.util.*;

public class Main
{
public static void main(String[] args)
{
Scanner sc = new Scanner(System.in);
while(true)
{
long x = sc.nextLong();
long xx = Math.abs(x);
if(x == 0)
{
break;
}
int result = 0;
for(int i = 32; i >= 1; i--)
{
if(i%2 == 0 && x < 0)
{
continue;
}
double m = Math.pow(xx,1.0/i);
int n1 = (int)Math.floor(m);
int n2 = (int)Math.ceil(m);
//System.out.println(i+ " " + m + " " + n1 + " " + n2);
if(Math.pow(n1,i) == xx || Math.pow(n2,i) == xx)
{
result = i;
break;
}
}
System.out.println(result);
}
}
}

1. 第23行：
hash = -1是否应该改成hash[s ] = -1

因为是要把从字符串s的start位到当前位在hash中重置

修改提交后能accept，但是不修改居然也能accept