README_EN.md

3. Longest Substring Without Repeating Characters

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Description

Given a string, find the length of the longest substring without repeating characters.

Example 1:

Input: "abcabcbb"

Output: 3 

Explanation: The answer is "abc", with the length of 3. 

Example 2:

Input: "bbbbb"

Output: 1

Explanation: The answer is "b", with the length of 1.

Example 3:

Input: "pwwkew"

Output: 3

Explanation: The answer is "wke", with the length of 3. 

             Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

Solutions

Python3

class Solution:
    def lengthOfLongestSubstring(self, s: str) -> int:
        res, chars = 0, dict()
        i = j = 0
        while j < len(s):
            if s[j] in chars:
                i = max(i, chars[s[j]] + 1)
            res = max(res, j - i + 1)
            chars[s[j]] = j
            j += 1
        return res

Java

class Solution {
    public int lengthOfLongestSubstring(String s) {
        int res = 0;
        Map<Character, Integer> chars = new HashMap<>();
        for (int i = 0, j = 0; j < s.length(); ++j) {
            char c = s.charAt(j);
            if (chars.containsKey(c)) {
                i = Math.max(i, chars.get(c) + 1);
            }
            chars.put(c, j);
            res = Math.max(res, j - i + 1);
        }
        return res;
    }
}

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