检查一个数字的二进制表示是否是回文
给定一个整数“x”，写一个 C 函数，如果 x 的二进制表示是回文，则返回 true，否则返回 false。 例如二进制表示为 10 的数字..01 是回文和数字，二进制表示为 10..00 不是回文。 这个想法类似于检查一个字符串是不是回文。我们从最左边和最右边的位开始，逐个比较位。如果发现不匹配，则返回 false。
算法: ispalindome(x) 1)使用 sizeof()运算符查找 x 中的位数。 2)将左右位置分别初始化为 1 和 n。 3)当左“l”小于右“r”时，执行以下操作。 ..…..a)如果“l”位置的位与“r”位置的位不同，则返回 false。 ..…..b)递增‘l’和递减‘r’，即做 l++和 r –-。 4)如果我们到达这里，这意味着我们没有发现一个不匹配的位。 找到给定位置的位，可以用类似这个帖子的思路。表达式“x&(1<<(k-1))”在从右数第 k 个位置的位被置位时给出非零值，在第 k 个位未被置位时给出零值。
下面是上述算法的实现。
C++
// C++ Program to Check if binary representation
// of a number is palindrome
#include<iostream>
using namespace std;
// This function returns true if k'th bit in x
// is set (or 1). For example if x (0010) is 2
// and k is 2, then it returns true
bool isKthBitSet(unsigned int x, unsigned int k)
{
return (x & (1 << (k - 1))) ? true : false;
}
// This function returns true if binary
// representation of x is palindrome.
// For example (1000...001) is palindrome
bool isPalindrome(unsigned int x)
{
int l = 1; // Initialize left position
int r = sizeof(unsigned int) * 8; // initialize right position
// One by one compare bits
while (l < r)
{
if (isKthBitSet(x, l) != isKthBitSet(x, r))
return false;
l++; r--;
}
return true;
}
// Driver Code
int main()
{
unsigned int x = 1 << 15 + 1 << 16;
cout << isPalindrome(x) << endl;
x = 1 << 31 + 1;
cout << isPalindrome(x) << endl;
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java Program to Check if binary representation
// of a number is palindrome
class GFG
{
// This function returns true if k'th bit in x
// is set (or 1). For example if x (0010) is 2
// and k is 2, then it returns true
static int isKthBitSet(long x, long k)
{
int rslt = ((x & (1 << (k - 1))) != 0) ? 1 : 0;
return rslt;
}
// This function returns true if binary
// representation of x is palindrome.
// For example (1000...001) is palindrome
static int isPalindrome( long x)
{
long l = 1; // Initialize left position
long r = (Integer.SIZE/8 )* 8; // initialize right position
// One by one compare bits
while (l < r)
{
if (isKthBitSet(x, l) != isKthBitSet(x, r))
{
return 0;
}
l++; r--;
}
return 1;
}
// Driver Code
public static void main (String[] args)
{
long x = 1 << 15 + 1 << 16 ;
System.out.println(isPalindrome(x));
x = (1 << 31) + 1 ;
System.out.println(isPalindrome(x));
}
}
// This code is contributed by AnkitRai01
Python 3
# python 3 Program to Check if binary representation
# of a number is palindrome
import sys
# This function returns true if k'th bit in x
# is set (or 1). For example if x (0010) is 2
# and k is 2, then it returns true
def isKthBitSet(x, k):
if ((x & (1 << (k - 1))) !=0):
return True
else:
return False
# This function returns true if binary
# representation of x is palindrome.
# For example (1000...001) is palindrome
def isPalindrome(x):
l = 1 # Initialize left position
r = 2 * 8 # initialize right position
# One by one compare bits
while (l < r):
if (isKthBitSet(x, l) != isKthBitSet(x, r)):
return False
l += 1
r -= 1
return True
# Driver Code
if __name__ =='__main__':
x = 1 << 15 + 1 << 16
print(int(isPalindrome(x)))
x = 1 << 31 + 1
print(int(isPalindrome(x)))
# This code is contributed by
# Surendra_Gangwar
C
// C# Program to Check if binary representation
// of a number is palindrome
using System;
class GFG
{
// This function returns true if k'th bit in x
// is set (or 1). For example if x (0010) is 2
// and k is 2, then it returns true
static int isKthBitSet(long x, long k)
{
int rslt = ((x & (1 << (int)(k - 1))) != 0) ? 1 : 0;
return rslt;
}
// This function returns true if binary
// representation of x is palindrome.
// For example (1000...001) is palindrome
static int isPalindrome( long x)
{
long l = 1; // Initialize left position
long r = 4 * 8; // initialize right position
// One by one compare bits
while (l < r)
{
if (isKthBitSet(x, l) != isKthBitSet(x, r))
{
return 0;
}
l++; r--;
}
return 1;
}
// Driver Code
public static void Main ()
{
long x = 1 << 15 + 1 << 16 ;
Console.WriteLine(isPalindrome(x));
x = (1 << 31) + 1 ;
Console.WriteLine(isPalindrome(x));
}
}
// This code is contributed by AnkitRai01
服务器端编程语言（Professional Hypertext Preprocessor 的缩写）
<?php
// PHP Program to Check if binary representation
// of a number is palindrome
// This function returns true if k'th bit in x
// is set (or 1). For example if x (0010) is 2
// and k is 2, then it returns true
function isKthBitSet($x, $k)
{
return ($x & (1 << ($k - 1))) ? true : false;
}
// This function returns true if binary
// representation of x is palindrome.
// For example (1000...001) is palindrome
function isPalindrome($x)
{
$l = 1; // Initialize left position
$r = sizeof(4) * 8; // initialize right position
// One by one compare bits
while ($l < $r)
{
if (isKthBitSet($x, $l) != isKthBitSet($x, $r))
return false;
$l++;
$r--;
}
return true;
}
// Driver Code
$x = 1 << 15 + 1 << 16;
echo isPalindrome($x), "\n";
$x = 1 << 31 + 1;
echo isPalindrome($x), "\n";
// This code is contributed by ajit.
?>
java 描述语言
<script>
// Javascript program to Check if binary
// representation of a number is palindrome
// This function returns true if k'th bit in x
// is set (or 1). For example if x (0010) is 2
// and k is 2, then it returns true
function isKthBitSet(x, k)
{
let rslt = ((x & (1 << (k - 1))) != 0) ? 1 : 0;
return rslt;
}
// This function returns true if binary
// representation of x is palindrome.
// For example (1000...001) is palindrome
function isPalindrome(x)
{
// Initialize left position
let l = 1;
// initialize right position
let r = 4 * 8;
// One by one compare bits
while (l < r)
{
if (isKthBitSet(x, l) !=
isKthBitSet(x, r))
{
return 0;
}
l++; r--;
}
return 1;
}
// Driver code
let x = 1 << 15 + 1 << 16;
document.write(isPalindrome(x) + "</br>");
x = (1 << 31) + 1;
document.write(isPalindrome(x));
// This code is contributed by divyesh072019
</script>
输出:
1
1
时间复杂度:0(x)
辅助空间:0(1)
本文由绍拉布·古普塔供稿。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。
版权属于：月萌API www.moonapi.com，转载请注明出处
