【LeetCode 0003】【滑动窗口】无重复字符的最长子串

3. Longest Substring Without Repeating Characters

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

Example 1:

**Input:** s = "abcabcbb"
**Output:** 3
**Explanation:** The answer is "abc", with the length of 3.

Example 2:

**Input:** s = "bbbbb"
**Output:** 1
**Explanation:** The answer is "b", with the length of 1.

Example 3:

**Input:** s = "pwwkew"
**Output:** 3
**Explanation:** The answer is "wke", with the length of 3.
Notice that the answer must be a substring, "pwke" is a subsequence and not a substring.

Constraints:

• 0 <= s.length <= 5 * 10^4
• s consists of English letters, digits, symbols and spaces.

JavaScript Solution

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function(s) {
    let ans = 0
    if('' === s){
        return ans
    }   
    let [left,right] = [0,-1]
    // matain the mapping from character to isPresent Flag 
    let flags = {}
    while(left < s.length){
        // mark all different elements as 1s
        if(( right+1 ) < s.length && !flags[s[right+1]] ){
            flags[s[ right+1 ]] = 1
            right++
            ans = Math.max(ans,right-left+1)
        }else{
            // sliding leftmost 1s to 0s
            flags[s[left]] = 0
            left++
        }
     }
    return ans
};