You are given two 32-bit numbers, N and M, and two bit positions, i and j. Write a method to set all bits between i and j in N equal to M (e.g., M becomes a substring of N located at i and starting at j).
Input : N = 1, M = 2, i = 2, j = 4 Output: 9 N = 00000001(Considering 8 bits only) M = 10 (Binary of 2) For more indexes, leading zeroes will be considered. Now set 3 bits from ith index to j in the N as in the M. Bits:- 0 0 0 (0 1 0) 0 1 = 9 Indexes:- 7 6 5 4 3 2 1 0 From index 2 to 4, bits are set according to the M.
Asked in : Adobe
A simple solution is to traverse all bits in N from 0 to 31 and set the bits equals to M in the range from i to j.
An efficient solution is to do following steps.
- Set all the bits after j in a number.
- Set all the bits before i in a number.
- Then perform Bitwise Or on both then we get the number with all the bits set except from i to j.
- Perform Bitwise And with the given N as to set the bits according to the N.
- Then shift M into the correct position i.e. in the range of i to j.
- And at the last perform Bitwise Or on (Shifted M and the N modifed in 4th step).
- The result will be N with M as substring from ith to jth bits
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