leetcode3: 无重复字符的最长字串

题目

class Solution {
    public int lengthOfLongestSubstring(String s) {
        if (s == null || s.length() == 0) return 0;
        int maxLen = 1;
        int curLen = 0;
        Map<Character, Integer> map = new HashMap<>();  //记录当前子串中每个字符出现的位置
        int i = 0;
        int n = s.length();
        char curChar;
        int lastIndex = -1;  //重复的字符上一次出现的位置
        while (i < n) {
            curChar = s.charAt(i);
            if (!map.containsKey(curChar) || map.get(curChar) < lastIndex) {
                curLen++;
                map.put(curChar, i);
            } else {
                lastIndex = map.get(curChar);
                maxLen = Math.max(curLen, maxLen);
                curLen = i - lastIndex;
                map.put(curChar, i);
            }
            i++;
        }
        maxLen = Math.max(curLen, maxLen);
        return maxLen;
    }
}