0003-longest-substring-without-repeating-characters 0008-string-to-integer-atoi 0011-container-with-most-water 0013-roman-to-integer 0017-letter-combinations-of-a-phone-number 0018-4sum 0020-valid-parentheses 0021-merge-two-sorted-lists 0022-generate-parentheses 0024-swap-nodes-in-pairs 0031-next...