Phone interview about general work history led to in person meeting. Question asked: In a given string find the last unique character. My answer was to filter out special cases (empty string, null string, blank string, single character string...) Some of this required firming up requirements (e.g. What do you return with a null string?) Interviewer's eyes rolled when I asked this and I was told to not worry about it, just code the answer. The actual coding was to be done on a whiteboard. My solution was to start from the end of the string and loop backwards. For each character compare the first index position against the last index position of the same character. If first and last index positions were the same the character was unique. Since I started from the end of the string the first time this happened was the last unique character. When that happened you dropped out of the loop and returned the answer. I was told that this was wrong. The way to do it was to run through the loop and hash the characters and keep track of the current last hash created. When you finished the loop the last hash created was the last unique character. We talked about the big O values of each method Overall the interview was difficult. The interviewer gave the impression their time was being wasted right from the start.