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A challenge string

A longest non-repeating sub-character string

Given a string, you find out which does not contain a sub-length of the longest string of repeated characters.

analysis:

When the hash table index record characters recent, i traversed position, seeking the current character position i is the longest non-repeating sub-string end.

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code：

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

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