3. 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.

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function(s) {
    if (s.length < 1) {
        return 0;
    }
    let current = 1;
    let result = 1;
    let tmp = s[0];
    for (let i = 1; i < s.length; i++) {
        let idx = tmp.indexOf(s[i]);
        tmp += s[i];
        if (idx < 0) {
            current++;
        } else {
            tmp = tmp.substring(idx + 1, tmp.length);
            current = tmp.length;
        }
        if (current >= result) {
            result = current;
        }
    }
    return result;
};

解题思路：子串一定是连续的字符串，因此当找到一个字符在“目前的子串”时，则重置该“目前的子串”，剔除重复字符之前的所有字符，然后继续查找，找到最终的结果。