3. 无重复字符的最长子串

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function(s) {
    let result = 1
    if (s.length === 0) return 0
    if (s.length === 1) return 1
    for(let i=0;i<s.length-1;i++){
        for(let j=i+1;j<s.length;j++){
            let arr = s.substr(i,j-i+1).split('')
            let set = new Set(arr)

            if(arr.length !==[...set].length){
                break
            } else {
                result = result >= arr.length ? result : arr.length
            }
        }
    }
    return result
};