xor

I'm trying to understand the binary operators in C# or in general, in particular ^ - exclusive or . For example: Given an array of positive integers. All numbers occur even number of times except one number which occurs odd number of times. Find the number in O(n) time and constant space. This can be done with ^ as follows: Do bitwise XOR of all the elements. Finally we get the number which has odd occurrences. How does it work? When I do: int res = 2 ^ 3; res = 1; int res = 2 ^ 5; res = 7; int res = 2 ^ 10; res = 8; What's actually happening? What are the other bit magics? Any reference I can

What operation does the following ‘C’ statement perform? star = star ^ 0b00100100; (A) Toggles bits 2 and 5 of the variable star. (B) Clears all bits except bits 2 and 5 of the variable star. (C) Sets all bits except bits 2 and 5 of the variable star. (D) Multiplies value in the variable star with 0b00100100. I'm still clueless about this. Can someone help me out? XOR operator (also called "logical addition") is defined like this: a b a^b ----------- 0 0 0 0 1 1 1 0 1 1 1 0 So a^0 leaves a intact while a^1 toggles it. For multiple-bit values, the operation is performed bitwise, i.e. between

We have an array A (say [1,2,3]) . We need to find the XOR(^)SUM of all pairs of integers in the array. Though this can easily be done in O(n^2) but how can i improve the complexity of the solution ? E.g for the above array , A, the answer would be (1^2)+(1^3)+(2^3) = 6 Thanks. You can separate the calculation to do one bit at a time. For example, look at the rightmost bit of all the numbers in the array. Suppose that a numbers have a rightmost 0-bit, and b numbers have a 1-bit. Then out of the pairs, a*b of them will have 1 in the rightmost bit of the XOR. This is because there are a*b ways

The problem is to find all the subarrays of the given array with xor of all its elements equal to zero. For example, if array contains elements [13,8,5,3,3] , the solution should give the indices of all subarrays like 0-2 , 3-4 , 0-4 , etc. The question is similar to the one asked here The only difference is that I want the indices of all the subarrays that satisfies the equation A0 xor A1 xor...xor An = 0 This is a fairly straightforward extension of the linked question. In Python, # Multivalued map from the XOR of array[:i] to i for all i. prefix_xor_to_stops = {0: [0]} prefix_xor = 0 for j,

Looking for a bit of regex help. I'd like to design an expression that matches a string with " foo " OR " bar ", but not both " foo " AND " bar " If I do something like... /((foo)|(bar))/ It'll match " foobar ". Not what I'm looking for. So, how can I make regex match only when one term or the other is present? Thanks! You can do this with a single regex but I suggest for the sake of readability you do something like... (/foo/ and not /bar/) || (/bar/ and not /foo/) This is what I use: /^(foo|bar){1}$/ See: http://www.regular-expressions.info/quickstart.html under repetition If your regex