Given a non-negative number n and two values l and r. The problem is to unset the bits in the range l to r in the binary representation of n, i.e, to unset bits from the rightmost lth bit to the rightmost rth bit.
Constraint: 1 <= l <= r <= number of bits in the binary representation of n.
Input : n = 42, l = 2, r = 5 Output : 32 (42)10 = (101010)2 (32)10 = (100000)2 The bits in the range 2 to 5 in the binary representation of 42 have been unset. Input : n = 63, l = 1, r = 4 Output : 48
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 bits in the range l to r in num. Refer this post.
- Now, perform n = n & num. This will unset the bits in the range l to r 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.
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