Given a non-negative number n. The problem is to unset the last m bits in the binary representation of n.
Constraint: 1 <= m <= num, where num is the number of bits in the binary representation of n.
Examples:
Input : n = 10, m = 2 Output : 8 (10)10 = (1010)2(8)10 = (1000)2 The last two bits in the binary representation of 10 have been unset. Input : n = 150, m = 4 Output : 144
Approach: Following are the steps:
- Calculate num = (1 << (sizeof(int) * 8 – 1)) – 1. This will produce the highest positive integer num. All the bits in num will be set.
- Toggle the last m bits in num. Refer this post.
- Now, perform n = n & num. This will unset the last m bits in n.
- Return n.
Note: The sizeof(int) has been used as input is of int data type. For large inputs you can use long int or long long int datatypes in place of int.
C++
// C++ implementation to unset bits the last m bits #include <bits/stdc++.h> using namespace std;
// function to toggle the last m bits unsigned int toggleLastMBits(unsigned int n,
unsigned int m)
{ // calculating a number 'num' having 'm' bits
// and all are set
unsigned int num = (1 << m) - 1;
// toggle the last m bits and return the number
return (n ^ num);
} // function to unset bits the last m bits unsigned int unsetLastMBits(unsigned int n,
unsigned int m)
{ // 'num' is the highest positive integer number
// all the bits of 'num' are set
unsigned int num = (1 << ( sizeof ( int ) * 8 - 1)) - 1;
// toggle the last 'm' bits in 'num'
num = toggleLastMBits(num, m);
// unset the last 'm' bits in 'n'
// and return the number
return (n & num);
} // Driver program to test above int main()
{ unsigned int n = 150, m = 4;
cout << unsetLastMBits(n, m);
return 0;
} |
Java
// Java implementation to unset // bits the last m bits class GFG
{ static int sizeofInt = 8 ;
// function to toggle the last m bits static int toggleLastMBits( int n,
int m)
{ // calculating a number 'num' having 'm' bits
// and all are set
int num = ( 1 << m) - 1 ;
// toggle the last m bits and return the number
return (n ^ num);
} // function to unset bits the last m bits static int unsetLastMBits( int n,
int m)
{ // 'num' is the highest positive integer number
// all the bits of 'num' are set
int num = ( 1 << (sizeofInt * 8 - 1 )) - 1 ;
// toggle the last 'm' bits in 'num'
num = toggleLastMBits(num, m);
// unset the last 'm' bits in 'n'
// and return the number
return (n & num);
} // Driver code public static void main(String[] args)
{ int n = 150 , m = 4 ;
System.out.println(unsetLastMBits(n, m));
} } /* This code is contributed by PrinciRaj1992 */ |
Python3
# Python3 implementation to unset # bits the last m bits import sys
# function to toggle the last m bits def toggleLastMBits (n, m):
# calculating a number 'num'
# having 'm' bits and all are set
num = ( 1 << m) - 1
# toggle the last m bits
# and return the number
return (n ^ num)
# function to unset bits # the last m bits def unsetLastMBits(n, m):
# 'num' is the highest positive integer
# number all the bits of 'num' are set
num = ( 1 << (sys.getsizeof( int ) * 8 - 1 )) - 1
# toggle the last 'm' bits in 'num'
num = toggleLastMBits(num, m)
# unset the last 'm' bits in 'n'
# and return the number
return (n & num)
# Driven code n = 150
m = 4
print (unsetLastMBits(n, m))
# This code is contributed by "rishabh_jain". |
C#
// C# implementation to unset // bits the last m bits using System;
class GFG
{ static int sizeofInt = 8;
// function to toggle the last m bits static int toggleLastMBits( int n,
int m)
{ // calculating a number 'num' having 'm' bits
// and all are set
int num = (1 << m) - 1;
// toggle the last m bits and return the number
return (n ^ num);
} // function to unset bits the last m bits static int unsetLastMBits( int n,
int m)
{ // 'num' is the highest positive integer number
// all the bits of 'num' are set
int num = (1 << (sizeofInt * 8 - 1)) - 1;
// toggle the last 'm' bits in 'num'
num = toggleLastMBits(num, m);
// unset the last 'm' bits in 'n'
// and return the number
return (n & num);
} // Driver code public static void Main(String[] args)
{ int n = 150, m = 4;
Console.WriteLine(unsetLastMBits(n, m));
} } // This code is contributed by Rajput-Ji |
PHP
<?php // php implementation to unset // bits the last m bits // function to toggle // the last m bits function toggleLastMBits( $n , $m )
{ // calculating a number 'num'
// having 'm' bits
// and all are set
$num = (1 << $m ) - 1;
// toggle the last m bits
// and return the number
return ( $n ^ $num );
} // function to unset bits // the last m bits function unsetLastMBits( $n , $m )
{ // 'num' is the highest positive
// integer number all the bits
// of 'num' are set
//4 is Size of integer 32 bit
$num = (1 << (4 * 8 - 1)) - 1;
// toggle the last 'm' bits in 'num'
$num = toggleLastMBits( $num , $m );
// unset the last 'm' bits in 'n'
// and return the number
return ( $n & $num );
} // Drivercode
$n = 150;
$m = 4;
echo unsetLastMBits( $n , $m );
// This code is contributed by mits ?> |
Javascript
<script> // JavaScript implementation to unset // bits the last m bits let sizeofLet = 8; // Function to toggle the last m bits function toggleLastMBits(n, m)
{ // Calculating a number 'num' having
// 'm' bits and all are set
let num = (1 << m) - 1;
// Toggle the last m bits and
// return the number
return (n ^ num);
} // Function to unset bits the last m bits function unsetLastMBits(n, m)
{ // 'num' is the highest positive
// integer number all the bits of
// 'num' are set
let num = (1 << (sizeofLet * 8 - 1)) - 1;
// Toggle the last 'm' bits in 'num'
num = toggleLastMBits(num, m);
// unset the last 'm' bits in 'n'
// and return the number
return (n & num);
} // Driver Code let n = 150, m = 4; document.write(unsetLastMBits(n, m)); // This code is contributed by sanjoy_62 </script> |
Output:
144
Time Complexity: O(1)
Auxiliary Space: O(1)
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