Description:
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.
思路：
利用HashMap，把字符当做key，把字符最后出现的index当做value存在map中，储存的过程其实就是在对字符串的遍历，当发现重复的字符时，更新结果。
Solution
public int longest_substring_without_repeating(String s){
int result = 0;
HashMap<Character, Integer> map = new HashMap<>(); //store the current index of the character
for(int i = 0, j = 0; j < s.length(); j++){
char cur_char = s.charAt(j);
if(map.containsKey(cur_char)){
i = Math.max(i, map.get(cur_char)+1);
}
map.put(cur_char, j);
result = Math.max(result, j - i + 1);
}
return result;
}