检查一个数字是否可以用幂表示|设置 2(使用对数)
原文:https://www . geesforgeks . org/check-number-can-expressed-power-set-2-use-log/
检查给定一个正整数 n，一个数是否可以表示为 x^y (x 升到 y 的幂) ，找出它是否可以表示为 x^y，其中 y > 1 和 x > 0。x 和 y 都是整数。 例:
Input: n = 8
Output: true
8 can be expressed as 2^3
Input: n = 49
Output: true
49 can be expressed as 7^2
Input: n = 48
Output: false
48 can't be expressed as x^y
我们在下面的帖子中讨论了两种不同的方法。 检查一个数是否可以表示为 x^y (x 的幂为 y) 。 思路是从 2 到 n 的平方根在不同的基数上求 Log n，如果一个基数的 Log n 变成整数，那么结果为真，否则结果为假。
C++
// CPP program to find if a number
// can be expressed as x raised to
// power y.
#include <bits/stdc++.h>
using namespace std;
bool isPower(unsigned int n)
{
// Find Log n in different bases
// and check if the value is an
// integer
for (int x=2; x<=sqrt(n); x++) {
float f = log(n) / log(x);
if ((f - (int)f) == 0.0)
return true;
}
return false;
}
// Driver code
int main()
{
for (int i = 2; i < 100; i++)
if (isPower(i))
cout << i << " ";
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to find if a number
// can be expressed as x raised to
// power y.
class GFG {
static boolean isPower(int n)
{
// Find Log n in different
// bases and check if the
// value is an integer
for (int x = 2; x <=
(int)Math.sqrt(n); x++)
{
float f = (float)Math.log(n) /
(float) Math.log(x);
if ((f - (int)f) == 0.0)
return true;
}
return false;
}
// Driver code
public static void main(String args[])
{
for (int i = 2; i < 100; i++)
if (isPower(i))
System.out.print( i + " ");
}
}
// This code is contributed by Sam007
Python 3
# Python3 program to find if a number
# can be expressed as x raised to
# power y.
import math
def isPower(n):
# Find Log n in different
# bases and check if the
# value is an integer
for x in range(2,int(math.sqrt(n)) + 1):
f = math.log(n) / math.log(x);
if ((f - int(f)) == 0.0):
return True;
return False;
# Driver code
for i in range(2, 100):
if (isPower(i)):
print(i, end = " ");
# This code is contributed by mits
C
// C# program to find if a number
// can be expressed as x raised to
// power y.
using System;
class GFG
{
static bool isPower(int n)
{
// Find Log n in different
// bases and check if the
// value is an integer
for (int x = 2;
x <= (int)Math.Sqrt(n); x++)
{
float f = (float)Math.Log(n) /
(float) Math.Log(x);
if ((f - (int)f) == 0.0)
return true;
}
return false;
}
// Driver Code
public static void Main()
{
for (int i = 2; i < 100; i++)
if (isPower(i))
Console.Write( i + " ");
}
}
// 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 if a number
// can be expressed as x raised to
// power y.
function isPower($n)
{
// Find Log n in different
// bases and check if the
// value is an integer
for ($x = 2; $x <= sqrt($n); $x++)
{
$f = log($n) / log($x);
if (($f - (int)$f) == 0.0)
return true;
}
return false;
}
// Driver code
for ($i = 2; $i < 100; $i++)
if (isPower((int)$i))
echo $i." ";
// This code is contributed by Sam007
?>
java 描述语言
<script>
// javascript program to find if a number
// can be expressed as x raised to
// power y.
function isPower(n) {
// Find Log n in different
// bases and check if the
// value is an integer
for (x = 2; x <= parseInt( Math.sqrt(n)); x++)
{
var f = Math.log(n) / Math.log(x);
if ((f - parseInt( f)) == 0.0)
return true;
}
return false;
}
// Driver code
for (i = 2; i < 100; i++)
if (isPower(i))
document.write(i + " ");
// This code contributed by Rajput-Ji
</script>
Output:
4 8 9 16 25 27 32 36 49 64 81
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