003.无重复字符的最长子串

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

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", 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.

给定一个字符串，找出不含有重复字符的最长子串的长度。

示例：

给定 "abcabcbb" ，没有重复字符的最长子串是 "abc" ，那么长度就是3。

给定 "bbbbb" ，最长的子串就是 "b" ，长度是1。

给定 "pwwkew" ，最长子串是 "wke" ，长度是3。请注意答案必须是一个子串，"pwke" 是 子序列  而不是子串

思路：准备一个dict来存储每个字母最新的位置，出现重复的则记录下该字母的

通俗版

class Solution(object):
    def lengthOfLongestSubstring(self,s):
        temp = res = ''
        for item in s:
            if item not in temp:
                temp += item
                if len(temp) > len(res):
                    res = temp
            else:
                i = temp.index(item)  # 找到该数据对应的索引
                if i == len(temp) - 1:  # 如果找到尾部了
                    temp = item  # 重新复制temp
                else:
                    temp = temp[i + 1:] + item
        return len(res)

下面是最简洁版的

def lengthOfLongestSubstring(s):
	d = {}
	start = 0
	ans = 0
	for i,c in enumerate(s):
		if c in d:
			start = max(start,d[c] + 1) # abba
		d[c] = i
		ans = max(ans,i - start + 1)
	return ans
print(lengthOfLongestSubstring('pwwkew'))