LeetCode ---3.Longest Substring Without Repeating Characters

public int lengthOfLongestSubstring(String s) {
    char[] chars = s.toCharArray();

    //存储已遍历的元素中相应char值最后出现的位置
    HashMap<Character, Integer> map = new HashMap<Character, Integer>();

    //当遍历到i位置时，lastNoRepeatIndex到i是已遍历元素中没有重复元素出现的部分
    //如：abcdeefghij，当遍历到g元素，lastNoRepeatIndex=5；即第二个e的位置
    int lastNoRepeatIndex = 0;

    //最长子串的前后位置下标
    int[] longestIndex = {0, 0};

    //最长子串长度
    int longestLength = 0;
    
    int len = 0;
    
    for(int i = 0; i < chars.length; i ++) {
        //abcdeefghiijk,遍历到i=10时，将lastNoRepeatIndex从5更新到10
        if(map.containsKey(chars[i]) && map.get(chars[i]) + 1 > lastNoRepeatIndex) {
            lastNoRepeatIndex = map.get(chars[i]) + 1;
        } 
        map.put(chars[i], i);
        len = i - lastNoRepeatIndex +1;
        if(len > longestLength) {
            longestLength = len;
            longestIndex[0] = lastNoRepeatIndex + 1;
            longestIndex[1] = i;
        }
    }
    return longestLength;
}