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

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 subsequence and not a substring.

/**
* 每次出现重复的字符的时候，计算两个字符之间的长度，和上一次保存的长度取最大值
* @param s
* @return
*/
public static int lengthOfLongestSubstring(String s) {
if (s.length()==0) return 0;
int max=0;
HashMap<Character, Integer> map = new HashMap<Character, Integer>();
for (int i=0, j=0; i<s.length(); ++i){
if (map.containsKey(s.charAt(i))){
j = Math.max(j,map.get(s.charAt(i))+1);
}
map.put(s.charAt(i),i);//每次更新了新出现从字符的位置
max = Math.max(max,i-j+1);
}
return max;
}