3. Longest Substring Without Repeating Characters
O(n^2)
from collections import defaultdict def solve(s): if not isinstance(s, str) or len(s) == 0: return 0 idx_set = defaultdict(set) s_len = len(s) res = '' for i in range(s_len): for i_index in range(s_len-i): if s[i_index + i] not in idx_set[i]: idx_set[i].add(s[i_index + i]) else: if len(res) < len(idx_set[i]): res = ''.join(idx_set[i]) break return res print solve('pwwkew')
solution 2: maintain a window:
def solve1(s): if not isinstance(s, str) or len(s) == 0: return '' the_list = list() res = '' for c in s: if c not in the_list: the_list.append(c) else: if len(res) < len(the_list): res = ''.join(the_list) the_list_copy = copy.deepcopy(the_list) for ts in the_list_copy: if ts == c: the_list.remove(ts) break else: the_list.remove(ts) the_list.append(c) if len(res) < len(the_list): res = ''.join(the_list) return res print solve1("pwwkew")