Amazon Software Developer Internship interview questions

There we 2 rounds (online) to be cleared before qualifying for a phone interview. First Round Consisted of an Aptitude Test with Questions such as find missing number in a Sequence of numbers, etc. It was Fairly easy . You need to score atleast 28/30 to qualify for the next round. Second Round- Here I had to Solve 2 coding problems within 70 mins. First problem-find if given set of parentheses is valid consisting of all types i.e. {[(. Second problem- reverse given linked list from the middle. I both problems I couldn't pass just 1 testcase hence was rejected