Most Powerful XOR

3.7

3 votes
Problem

Given two integers, L and R, find the maximal value of A xor B, where A and B satisfy the following condition:

L ≤ A ≤ B ≤ R

Input Format:

First line contains T,number of test cases following T lines containing 2 intergers L and R ; L is present in the first line and R in the second line.

Output Format:

T lines containing the maximal value as mentioned in the problem statement.

Constraints: 

1≤L≤R≤103

Time Limit: 1
Memory Limit: 256
Source Limit:
Explanation

The input tells us that L=10 and R=15. All the pairs which comply to above condition are the following: 

10⊕10=0 10⊕11=1 10⊕12=6 10⊕13=7 10⊕14=4 10⊕15=5 11⊕11=0 11⊕12=7 11⊕13=6 11⊕14=5 11⊕15=4 12⊕12=0 12⊕13=1 12⊕14=2 12⊕15=3 13⊕13=0 13⊕14=3 13⊕15=2 14⊕14=0  14⊕15=1  15⊕15=0 

Here two pairs (10, 13) and (11, 12) have maximum xor value 7, and this is the answer.

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