[LeetCode] 3. Longest Substring Without Repeating Characters

https://leetcode.com/problems/longest-substring-without-repeating-characters/description/

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

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", the answer is "wke", with the length of 3. Note that the answer must be a substring, "pwke" is a subsequenceand not a substring.

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

 

Previously failed case: start should always be greater than previous start

Input:
"abba"
Output:
3
Expected:
2