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3. Longest Substring Without Repeating Characters
Medium
Given a string s, find the length of the longest substring without repeating characters.
Example 1:
Input: s = “abcabcbb”
Output: 3
Explanation: The answer is “abc”, with the length of 3.
Example 2:
Input: s = “bbbbb”
Output: 1
Explanation: The answer is “b”, with the length of 1.
Example 3:
Input: s = “pwwkew”
Output: 3
Explanation: The answer is “wke”, with the length of 3. Notice that the answer must be a substring, “pwke” is a subsequence and not a substring.
Example 4:
Input: s = “”
Output: 0
Constraints:
0 <= s.length <= 5 * 104sconsists of English letters, digits, symbols and spaces.
Solution
# @param {String} s
# @return {Integer}
def length_of_longest_substring(s)
last_indices = Array.new(256, -1)
max_len = 0
cur_len = 0
start = 0
s.each_char.with_index do |cur, i|
cur = cur.ord
if last_indices[cur] < start
last_indices[cur] = i
cur_len += 1
else
last_index = last_indices[cur]
start = last_index + 1
cur_len = i - start + 1
last_indices[cur] = i
end
max_len = cur_len if cur_len > max_len
end
max_len
end