Nyoj 744 ant financial problems (1)

Ant's problem (I) time limit: 1000 MS | memory limit: 65535 kb difficulty: 2

Description

Little ant shoes recently fell in love with bit operations, and he felt that bit operations were amazing. However, he encountered a problem recently:

Given a range [a, B], we can look for two numbers x and y in the range to make X exclusive or y the largest. Come on, help him!

Input

There are multiple groups of test data (ended with EOF ).
Enter two numbers A and B for each group of data (0 <= A <B <2 ^ 63)

Output

Outputs An exclusive or maximum value between A and B.

Sample Input

1 28 9

Sample output

31

Ideas:

Multiple Data tests show that each output result is 2 ^ n-1, and the relationship between N and A and B is required. This topic guides us to use bitwise operations,

Take the number of two groups, for example, 4 or 8. The calculated range is 7 ^ 8 = 15 = (1111) 2 = 2 ^ 4-1;
Search for a group of 2, 6 at will, and calculate the range of 2 ^ 5 = 7 = (111) 2 = 2 ^ 3-1;

Through the above analysis, we can know that the maximum value is 2 ^ n-1, and N is the binary number of The number of right boundary.

Therefore, you can think of the following code:

# Include <stdio. h> int main () {long a, B, X; // use the long type while (~ Scanf ("% LLD", & A, & B) {x = a ^ B; // find the number of digits int CNT = 0; while (x) ++ CNT, x> = 1; // calculate the number of digits of printf ("% LLD \ n", (1ll) <CNT)-1 ); // obtain 2 ^ CNT-1;} return 0 ;}

Nyoj 744 ant financial problems (1)