原题

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.

public class Solution {
    public int lengthOfLongestSubstring(String s) {
        if (s == null || s.length() == 0) {
            return 0;
        }
        int[] map = new int[128];
        int len = 0;
        int mark = 0;
        for (int i = 0; i < s.length(); i++) {
            char c = s.charAt(i);
            if (map[c] > mark) {
                mark = map[c];
            }
            int currLen = i - mark + 1;
            if (currLen > len) {
                len = currLen;
            }
            map[c] = i + 1;
        }
        return len ;
    }
}