The code for day 1 that finds entries that sum to 2020 assumes that every entry is unique. However, this assumtion is not supported by the assignment, so it doesn't find the answer in the case that the expense report contains the number 1010 twice (which isn't even that unlikely for an expenses report).
The code for day 1 that finds entries that sum to 2020 assumes that every entry is unique. However, this assumtion is not supported by the assignment, so it doesn't find the answer in the case that the expense report contains the number 1010 twice (which isn't even that unlikely for an expenses report).