Leetcode3 Longest Substring Without Repeating Characters-蒲公英云

Leetcode3 Longest Substring Without Repeating Characters

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.

class Solution { 
    public int lengthOfLongestSubstring(String s) { 
        // 使用set进行存储。
        Set<Character> set =new HashSet<>();
        // 设置 i ,j 为左右指针。
        int i=0,j=0,max=0;
        while(j<s.length())
        { 
            // 如果没有右指针指向的元素
            if(!set.contains(s.charAt(j)))
            { 
                // 把右指针的元素加入。并移动指针。
                set.add(s.charAt(j));
                j++;
                max =Math.max(max,set.size());
            }
            // 如果有右指针指向的元素 ，把左指针指向的元素删除，并且移动左指针，
            // 当下次循环时，如果判断还是有右指针指向的元素，
            //会继续把左指针指向的元素删除，并且移动左指针,直到没有。
            else
            { 
                set.remove(s.charAt(i));
                i++;
            }
        }
        return max;
    }
}