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.
Solution
- 维护一个没有重复字符的sliding window -> [left,i]
- 遍历数组，对每一个<index,character>更新sliding window的左侧边界
- left = MAX(上一次出现这个字符串的地方, left)
-
输出其中最大窗口的长度
- 使用一个hashmap记录每个字符上次出现的地方，使用一个int变量记录当前最大的窗口长度
Code (JAVA)
public int lengthOfLongestSubstring(String s) {
// <char, last time appear index>
Map<Character, Integer> indexing = new HashM();
int left = -1, max = 0;
for(int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
left = Math.max(left, indexingetOrDefault(c,-1));
max = Math.max(max, i - left);
indexing.put(c,i);
}
return max;
}
