给定数字n，任务是仅切换数字的第一位和最后一位
例子 ：
Input : 10
Output : 3
Binary representation of 10 is
1010. After toggling first and
last bits, we get 0011.
Input : 15
Output : 6先决条件：找到给定号码的MSB。
1)生成一个数字，该数字包含已设置的第一位和最后一位。我们需要将所有中间位更改为0，并将转角位保持为1。
2)答案是生成的数字和原始数字的XOR。
C++
// CPP program to toggle first and last
// bits of a number
#include
using namespace std;
// Returns a number which has same bit
// count as n and has only first and last
// bits as set.
int takeLandFsetbits(int n)
{
// set all the bit of the number
n |= n >> 1;
n |= n >> 2;
n |= n >> 4;
n |= n >> 8;
n |= n >> 16;
// Adding one to n now unsets
// all bits and moves MSB to
// one place. Now we shift
// the number by 1 and add 1.
return ((n + 1) >> 1) + 1;
}
int toggleFandLbits(int n)
{
// if number is 1
if (n == 1)
return 0;
// take XOR with first and
// last set bit number
return n ^ takeLandFsetbits(n);
}
// Driver code
int main()
{
int n = 10;
cout << toggleFandLbits(n);
return 0;
} Java
// Java program to toggle first and last
// bits of a number
import java.io.*;
class GFG {
// Returns a number which has same bit
// count as n and has only first and last
// bits as set.
static int takeLandFsetbits(int n)
{
// set all the bit of the number
n |= n >> 1;
n |= n >> 2;
n |= n >> 4;
n |= n >> 8;
n |= n >> 16;
// Adding one to n now unsets
// all bits and moves MSB to
// one place. Now we shift
// the number by 1 and add 1.
return ((n + 1) >> 1) + 1;
}
static int toggleFandLbits(int n)
{
// if number is 1
if (n == 1)
return 0;
// take XOR with first and
// last set bit number
return n ^ takeLandFsetbits(n);
}
// Driver code
public static void main(String args[])
{
int n = 10;
System.out.println(toggleFandLbits(n));
}
}
/*This code is contributed by Nikita Tiwari.*/Python3
# Python 3 program to toggle first
# and last bits of a number.
# Returns a number which has same bit
# count as n and has only first and last
# bits as set.
def takeLandFsetbits(n) :
# set all the bit of the number
n = n | n >> 1
n = n | n >> 2
n = n | n >> 4
n = n | n >> 8
n = n | n >> 16
# Adding one to n now unsets
# all bits and moves MSB to
# one place. Now we shift
# the number by 1 and add 1.
return ((n + 1) >> 1) + 1
def toggleFandLbits(n) :
# if number is 1
if (n == 1) :
return 0
# take XOR with first and
# last set bit number
return n ^ takeLandFsetbits(n)
# Driver code
n = 10
print(toggleFandLbits(n))
# This code is contributed by Nikita Tiwari.C#
// C# program to toggle first and last
// bits of a number
using System;
class GFG {
// Returns a number which has same bit
// count as n and has only first and last
// bits as set.
static int takeLandFsetbits(int n)
{
// set all the bit of the number
n |= n >> 1;
n |= n >> 2;
n |= n >> 4;
n |= n >> 8;
n |= n >> 16;
// Adding one to n now unsets
// all bits and moves MSB to
// one place. Now we shift
// the number by 1 and add 1.
return ((n + 1) >> 1) + 1;
}
static int toggleFandLbits(int n)
{
// if number is 1
if (n == 1)
return 0;
// take XOR with first and
// last set bit number
return n ^ takeLandFsetbits(n);
}
// Driver code
public static void Main()
{
int n = 10;
Console.WriteLine(toggleFandLbits(n));
}
}
// This code is contributed by Anant Agarwal.PHP
> 1;
$n |= $n >> 2;
$n |= $n >> 4;
$n |= $n >> 8;
$n |= $n >> 16;
// Adding one to n now unsets
// all bits and moves MSB to
// one place. Now we shift
// the number by 1 and add 1.
return (($n + 1) >> 1) + 1;
}
function toggleFandLbits(int $n)
{
// if number is 1
if ($n == 1)
return 0;
// take XOR with first and
// last set bit number
return $n ^ takeLandFsetbits($n);
}
// Driver code
$n = 10;
echo toggleFandLbits($n);
// This code is contributed by mits
?>Javascript
输出 ：
3时间复杂度为O(1)。