Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
Given is an array of integers. Each number in the array repeats an ODD number of times, but only 1 number is repeated for an EVEN number of times. Find that number.
I was thinking a hash map, with each element’s count. It requires O(n) space. Is there a better way?
Hash-map is fine, but all you need to store is each element’s count modulo 2.
All of those will end up being 1 (odd) except for the 0 (even) -count element.
(As Aleks G says you don’t need to use arithmetic (
count++ %2), only xor (count ^= 0x1); although any compiler will optimize that anyway.)