Arrays Third max https://rohitm17.medium.com/leetcode-414-third-maximum-number-410028e7f921 Patterns https://www.youtube.com/watch?v=RYT08CaYq6A Others https://stackoverflow.com/questions/12134687/how-to-add-element-into-arraylist-in-hashmap https://www.quora.com/How-do-you-add-an-element-to-an-arraylist-thats-in-a-hashmap https://web.stanford.edu/class/archive/cs/cs108/cs108.1092/handouts/02SCollections.pdf https://coderanch.com/t/529935/java/Adding-values-list-existing-key https://onecompiler.com/java/3urmp9w25