Leetcode question brushing (question 3) - the longest substring without repeated characters

One 、 Title Description
Given a string s , Please find out that there are no duplicate characters in it Longest substrings The length of .
Two 、 Example

 Example 1 ：
 Input : s = "abcabcbb"
 Output : 3 
 explain :  Because the longest substring without repeating characters is  "abc", So its length is  3.

 Example 2 ：
 Input : s = "bbbbb"
 Output : 1
 explain :  Because the longest substring without repeating characters is  "b", So its length is  1.

3、 ... and 、 Ideas
You can use two pointers left and right The pointer , The right pointer traverses each subscript of the current string , And use a hash table to save the value of the current string and its subscript . If the current value is already in map in , And the subscript of the repeated value is greater than or equal to left Value , At this point, you need to move the left pointer , Move it to the next digit of the duplicate value . And then I kept going map Put values in ( If it is repeated, it will be overwritten ), And constant calculation max Value .
Four 、 Code

/** * @param {string} s * @return {number} */
var lengthOfLongestSubstring = function(s) {
    
    let left = 0;
    let max = 0;
    let map = new Map()
    let length = s.length
    for(let right = 0; right < length; right++) {
    
        if(map.has(s[right]) && map.get(s[right]) >= left) {
    
            left = map.get(s[right]) + 1
        }
        map.set(s[right], right)
        max = Math.max(max, right - left + 1)
    }
    return max
};

5、 ... and 、 analysis
The time complexity is O（n）, The space complexity is O(n).