PayPal Software Engineer(Internship) interview questions

Phone call 1 review resume , algo questions:deleting multiple appearances of same character in the string, in a binary tree with negative and positive values find the largest product subtree. phone call .He also asked me java synchronization,lock,threads. Day 2:interviewer1 convert roman numbers into integer numbers interviewer2 some sorting problem , explain the inner working of the sort function used i used java arrays.sort , so she asked me what is the inner implementation of it manager:behavioral questions :what some challenges you faced while working in a team and how did you overcome it?

Data structures and algorithms