Maximum Xor Problem

#1

Please explain the Editorial i am not understanding it.

#2

An efficient solution is to consider pattern of binary values from L to R. We can see that first bit from L to R either changes from 0 to 1 or it stays 1 i.e. if we take the XOR of any two numbers for maximum value their first bit will be fixed which will be same as first bit of XOR of L and R itself. After observing the technique to get first bit, we can see that if we XOR L and R, the most significant bit of this XOR will tell us the maximum value we can achieve i.e. let XOR of L and R is 1xxx where x can be 0 or 1 then maximum XOR value we can get is 1111 because from L to R we have all possible combination of xxx and it is always possible to choose these bits in such a way from two numbers such that their XOR becomes all 1.
Here is the code https://ide.codingblocks.com/s/239341

#3

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#4

I was not able to understand this problem so i came to this page…can u elaborate more because i want to know the reason that why are u subtracting 1 from the result??

#5

@keshavgupta0103 please do respnd

#6

for example if the maximum xor is 7, then the result formed by taking powers of 2 would be 8. so answer would be 8-1 = 7.

1 Like
#7

thanks…i got it now .

#8

when we get the msb why not we calculate (2^msb) -1.