寻找第 n 个幻数
幻数被定义为可以表示为 5 的幂或 5 的唯一幂之和的数。前几个神奇的数字是 5，25，30(5 + 25)，125，130(125 + 5)，…。 写函数求第 n 个幻数。 示例:
Input: n = 2
Output: 25
Input: n = 5
Output: 130
如果我们仔细注意，幻数可以表示为 001、010、011、100、101、110 等，其中 001 是 0 幂(5，3)+0 幂(5，2)+1 *幂(5，1)。所以基本上我们需要给定整数 n 中的每一个位集加 5 的幂。 下面是基于这个思想的实现。
C++
// C++ program to find nth magic number
#include <bits/stdc++.h>
using namespace std;
// Function to find nth magic number
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 语言(一种计算机语言，尤用于创建网站)
// Java program to find nth
// magic number
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
Python 3
# Python program to find nth magic number
# Function to find nth magic number
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 number
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
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// PHP program to find nth
// magic number
// Function to find nth
// magic number
function 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 Code
$n = 5;
echo "nth magic number is ",
nthMagicNo($n), "\n";
// This code is contributed by Ajit.
?>
java 描述语言
<script>
// Javascript program to find nth
// magic number
// 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));
</script>
输出:
nth magic number is 130
感谢曼拉辛格提出上述解决方案。
本文由 Abhay 供稿。如果你发现任何不正确的地方，或者你想分享更多关于上面讨论的话题的信息，请写评论。
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