查找第n个幻数

魔数定义为一个数字，可以表示为5的幂或5的唯一幂的总和。前几个幻数为5、25、30(5 + 25)，125、130(125 + 5)， …。
编写函数以查找第n个幻数。
例子：

Input: n = 2
Output: 25

Input: n = 5
Output: 130 

如果我们仔细注意魔术数字可以表示为001、010、011、100、101、110等，其中001是0 * pow(5,3)+ 0 * pow(5,2)+ 1 * pow(5 ，1)。因此，基本上，我们需要为给定整数n中的每个位加5的幂。
以下是基于此思想的实现。

C++

// C++ program to find nth magic numebr
#include 
using namespace std;
 
// Function to find nth magic numebr
int nthMagicNo(int n)
{
    int pow = 1, answer = 0;
 
    // Go through every bit of n
    while (n)
    {
       pow = pow*5;
 
       // If last bit of n is set
       if (n & 1)
         answer += pow;
 
       // proceed to next bit
       n >>= 1;  // or n = n/2
    }
    return answer;
}
 
// Driver program to test above function
int main()
{
    int n = 5;
    cout << "nth magic number is " << nthMagicNo(n) << endl;
    return 0;
}

Java

// Java program to find nth
// magic numebr
import java.io.*;
 
class GFG
{
  // Function to find nth magic number
  static int nthMagicNo(int n)
  {
     int pow = 1, answer = 0;
  
     // Go through every bit of n
     while (n != 0)
     {
       pow = pow*5;
  
       // If last bit of n is set
       if ((int)(n & 1) == 1)
         answer += pow;
  
       // proceed to next bit
       // or n = n/2
       n >>= 1; 
     }
     return answer;
  }
  
  // Driver program to test
  // above function
  public static void main(String[] args)
  {
    int n = 5;
    System.out.println("nth magic" +
    " number is " + nthMagicNo(n));
  }
}
 
 
// This code is contributed by
// prerna saini

Python3

# Python program to find nth magic numebr
 
# Function to find nth magic numebr
def nthMagicNo(n):
 
    pow = 1
    answer = 0
 
    # Go through every bit of n
    while (n):
 
        pow = pow*5
 
        # If last bit of n is set
        if (n & 1):
            answer += pow
 
        # proceed to next bit
        n >>= 1 # or n = n/2
     
    return answer
 
 
# Driver program to test above function
n = 5
print("nth magic number is", nthMagicNo(n))
 
# This code is contributed by
# Smitha Dinesh Semwal

C#

// C# program to find nth
// magic numebr
using System;
 
public class GFG
{
     
// Function to find nth magic number
static int nthMagicNo(int n)
{
    int pow = 1, answer = 0;
 
    // Go through every bit of n
    while (n != 0)
    {
        pow = pow * 5;
 
        // If last bit of n is set
        if ((int)(n & 1) == 1)
            answer += pow;
     
        // proceed to next bit
        // or n = n/2
        n >>= 1;
    }
    return answer;
}
 
// Driver Code
public static void Main()
{
    int n = 5;
    Console.WriteLine("nth magic" +    " number is "
                       + nthMagicNo(n));
 
}
}
 
// This code is contributed by Sam007

PHP

>= 1; // or $n = $n/2
    }
    return $answer;
}
 
// Driver Code
$n = 5;
echo "nth magic number is ",
       nthMagicNo($n), "\n";
 
// This code is contributed by Ajit.
?>

Javascript

 
    // Javascript program to find nth
    // magic numebr
     
    // Function to find nth magic number
    function nthMagicNo(n)
    {
        let pow = 1, answer = 0;
 
        // Go through every bit of n
        while (n != 0)
        {
            pow = pow * 5;
 
            // If last bit of n is set
            if ((n & 1) == 1)
                answer += pow;
 
            // proceed to next bit
            // or n = n/2
            n >>= 1;
        }
        return answer;
    }
     
    let n = 5;
    document.write("nth magic" + " number is " + nthMagicNo(n));
     

输出 ：

nth magic number is 130 

感谢manrajsingh提出上述解决方案。