在最高有效位之后切换所有位

给定一个数字，请在最高有效位(包括最高有效位)之后切换其所有位。

例子 ：

Input : 10 
Output : 5
Binary representation of 10 is 1010
After toggling we get 0101

Input : 5
Output : 2

我们可以通过将其与1进行XOR来切换一位(请注意1 ^ 0 = 1和1 ^ 1 = 0)。这个想法是采用仅设置一位的数字温度。逐一将温度的唯一设定位向左移动，并与n进行XOR运算，直到它超过n的MSB(最高有效位)为止。

C++

// CPP program to toggle set  bits starting
// from MSB
#include
using namespace std;
 
void toggle(int &n)
{
    // temporary variable to
    // use XOR with one of a n
    int temp = 1;
 
    // Run loop until the only
    // set bit in temp crosses
    // MST of n.
    while (temp <= n)
    {
        // Toggle bit of n
        // corresponding to
        // current set bit in
        // temp.
        n = n ^ temp;
 
        // Move set bit to next
        // higher position.
        temp = temp << 1;
    }
}
 
// Driver code
int main()
{
    int n = 10;
    toggle(n);
    cout << n;
    return 0;
}

Java

// Java program to toggle set
// bits starting from MSB
 
class GFG {
     
static int toggle(int n) {
     
    // temporary variable to
    // use XOR with one of a n
    int temp = 1;
 
    // Run loop until the only
    // set bit in temp crosses
    // MST of n.
    while (temp <= n) {
         
    // Toggle bit of n
    // corresponding to
    // current set bit in
    // temp.
    n = n ^ temp;
 
    // Move set bit to next
    // higher position.
    temp = temp << 1;
    }
    return n;
}
 
// Driver code
public static void main(String arg[])
{
    int n = 10;
    n = toggle(n);
    System.out.print(n);
}
}
 
// This code is contributed by Anant Agarwal.

Python3

# Python program to toggle
# set  bits starting
# from MSB
 
def toggle(n):
 
    # temporary variable to
    # use XOR with one of a n
    temp = 1
  
    #Run loop until the only
    #set bit in temp crosses
    #MST of n.
    while (temp <= n):
     
        # Toggle bit of n
        # corresponding to
        # current set bit in
        # temp.
        n = n ^ temp
  
        # Move set bit to next
        # higher position.
        temp = temp << 1
 
    return n
  
# Driver code
 
n = 10
n=toggle(n)
print(n)
 
# This code is contributed
# by Anant Agarwal.

C#

// C# program to toggle set
// bits starting from MSB
using System;
 
class GFG {
 
// Function to toggle bits
// starting from MSB   
static int toggle(int n) {
     
    // temporary variable to
    // use XOR with one of a n
    int temp = 1;
 
    // Run loop until the only
    // set bit in temp crosses
    // MST of n.
    while (temp <= n) {
         
    // Toggle bit of n
    // corresponding to
    // current set bit in
    // temp.
    n = n ^ temp;
 
    // Move set bit to next
    // higher position.
    temp = temp << 1;
    }
    return n;
}
 
// Driver code
public static void Main()
{
    int n = 10;
    n = toggle(n);
    Console.Write(n);
}
}
 
// This code is contributed by Nitin Mittal.

Javascript

 
// Javascript program to toggle set
// bits starting from MSB
function toggle(n)
{
     
    // Temporary variable to
    // use XOR with one of a n
    let temp = 1;
 
    // Run loop until the only
    // set bit in temp crosses
    // MST of n.
    while (temp <= n)
    {
         
        // Toggle bit of n
        // corresponding to
        // current set bit in
        // temp.
        n = n ^ temp;
 
        // Move set bit to next
        // higher position.
        temp = temp << 1;
    }
    return n;
}
 
// Driver code
let n = 10;
n = toggle(n);
 
document.write(n);
 
// This code is contributed by subham348
 

输出 ：

5

在数字以32位存储的假设下，可以优化上述解决方案以使其在O(1)时间内工作。

C++

// CPP program to toggle set  bits starting
// from MSB
#include
using namespace std;
 
// Returns a number which has all set bits
// starting from MSB of n
int setAllBitsAfterMSB(int n)
{   
    // This makes sure two bits
    // (From MSB and including MSB)
    // are set
    n |= n>>1;
 
    // This makes sure 4 bits
    // (From MSB and including MSB)
    // are set
    n |= n>>2;  
 
    n |= n>>4; 
    n |= n>>8;
    n |= n>>16;
    return n;
}
 
void toggle(int &n)
{
    n = n ^ setAllBitsAfterMSB(n);
}
 
// Driver code
int main()
{
    int n = 10;
    toggle(n);
    cout << n;
    return 0;
}

Java

// Java program to toggle set bits
// starting from MSB
 
class GFG {
     
// Returns a number which has all
// set bits starting from MSB of n
static int setAllBitsAfterMSB(int n) {
     
    // This makes sure two bits
    // (From MSB and including MSB)
    // are set
    n |= n >> 1;
 
    // This makes sure 4 bits
    // (From MSB and including MSB)
    // are set
    n |= n >> 2;
 
    n |= n >> 4;
    n |= n >> 8;
    n |= n >> 16;
    return n;
}
static int toggle(int n)
{
    n = n ^ setAllBitsAfterMSB(n);
    return n;
}
 
// Driver code
public static void main(String arg[])
{
    int n = 10;
    n = toggle(n);
    System.out.print(n);
}
}
 
// This code is contributed by Anant Agarwal.

Python3

# Python program to toggle set  bits starting
# from MSB
 
# Returns a number which has all set bits
# starting from MSB of n
def setAllBitsAfterMSB(n):
  
    # This makes sure two bits
    # (From MSB and including MSB)
    # are set
    n |= n>>1
  
    # This makes sure 4 bits
    # (From MSB and including MSB)
    # are set
    n |= n>>2  
  
    n |= n>>4 
    n |= n>>8
    n |= n>>16
    return n
 
def toggle(n):
 
    n = n ^ setAllBitsAfterMSB(n)
    return n
     
#Driver code
 
n = 10
n=toggle(n)
print(n)
# This code is contributed by Anant Agarwal.

C＃

// C# program to toggle set bits
// starting from MSB
using System;
 
class GFG {
         
    // Returns a number which has all
    // set bits starting from MSB of n
    static int setAllBitsAfterMSB(int n)
    {
         
        // This makes sure two bits
        // (From MSB and including MSB)
        // are set
        n |= n >> 1;
     
        // This makes sure 4 bits
        // (From MSB and including MSB)
        // are set
        n |= n >> 2;
     
        n |= n >> 4;
        n |= n >> 8;
        n |= n >> 16;
        return n;
    }
     
    static int toggle(int n)
    {
        n = n ^ setAllBitsAfterMSB(n);
        return n;
    }
     
    // Driver code
    public static void Main()
    {
        int n = 10;
        n = toggle(n);
        Console.WriteLine(n);
    }
}
 
// This code is contributed by Sam007.

的PHP

> 1;
 
    // This makes sure 4 bits
    // (From MSB and including MSB)
    // are set
    $n |= $n >> 2;
 
    $n |= $n >> 4;
    $n |= $n >> 8;
    $n |= $n >> 16;
    return $n;
}
function toggle(&$n)
{
    $n = $n ^ setAllBitsAfterMSB($n);
}
 
// Driver Code
$n = 10;
toggle($n);
echo $n;
 
// This code is contributed by ajit
?>

Java脚本

 
// Javascript program to toggle set  bits starting
// from MSB
 
// Returns a number which has all set bits
// starting from MSB of n
function setAllBitsAfterMSB(n)
{   
    // This makes sure two bits
    // (From MSB and including MSB)
    // are set
    n |= n>>1;
 
    // This makes sure 4 bits
    // (From MSB and including MSB)
    // are set
    n |= n>>2;  
 
    n |= n>>4; 
    n |= n>>8;
    n |= n>>16;
    return n;
}
 
function toggle(n)
{
    n = n ^ setAllBitsAfterMSB(n);
    return n;
}
 
// Driver code
    let n = 10;
    document.write(toggle(n));
 

输出 ：

5

感谢Devanshu Agarwal提出了这种方法。