无重复字符的最长子串|博客系列

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function(s) {
    if (typeof s !== 'string' || s.length <= 0) return 0;
    let charts = s.split('') // 字符串转数组
    let maxLength = 0
    let leftIndex = 0 // 记录每一次重复的位置
    for (let start = 0; start < charts.length; start++) {
        for (let i = leftIndex; i < start; i++) {
            if (charts[i] == charts[start]) { // 若是有相同的字符串
                maxLength = Math.max(maxLength, start - leftIndex)
                leftIndex = i + 1 // 更新重复位置的下标
                break // 跳出本次循环
            }
        }
    }
    return Math.max(maxLength, charts.length - leftIndex)
};

/**
 * @param {string} s
 * @return {number}
 */
var lengthOfLongestSubstring = function(s) {
  	if (typeof s !== 'string' || s.length <= 0) return 0;
    var start = 0,
        maxLength = 0,
        leftIndex = 0;
    for (let j = 0; j < s.length; j++) {
        leftIndex = s.slice(start, j).indexOf(s[j])
        if (leftIndex == -1) {
            maxLength = Math.max(maxLength, j - start + 1)
        } else {
            start += leftIndex + 1
        }
    }
    return maxLength;
};

lengthOfLongestSubstring('abcabcbd')
// 3