无重复字符的最长字符串

题目:https://leetcode-cn.com/problems/longest-substring-without-repeating-characters/

给定一个字符串,请你找出其中不含有重复字符的 最长子串 的长度。

法一:

def lengthOfLongestSubstring(s):
    listi = []
    if len(s) in [0,1]:
        return len(s)
    else:
        for i in range(len(s)):
            j = i
            while j < len(s)-1:
                j = j + 1
                r = s[i:j]
                if s[j] in r:
                    maxlen = len(r)
                    listi.append(maxlen)
                    break
                else:
                    maxlen = len(r)+1
                    listi.append(maxlen)
        return max(listi)

if __name__ == '__main__':
    s = ""
    print(lengthOfLongestSubstring(s))

思路: 无脑遍历,( 0 or 1)不好用,不知道为什么

给变量起名字时不要起list,max和函数名一致的,否则报错

法二:

def lengthOfLongestSubstring(s):
    """
    :type s: str
    :rtype: int
    """
    start = maxLength = 0
    usedChar = {}
    for index, char in enumerate(s):
        if char in usedChar and start <= usedChar[char]:
            start = usedChar[char] + 1   # 将值加1
        else:
            maxLength = max(maxLength, index - start + 1)
        usedChar[char] = index
    return maxLength

if __name__ == '__main__':
    s = 'abcdecb'
    print(lengthOfLongestSubstring(s))

思路:方法比较难

不断判断新的元素是否是已经存在于usedChar字典中,若存在,则将start指向已经存在的位置,继续遍历,否则判断长度,求max




posted on 2019-05-05 10:29  吃我一枪  阅读(277)  评论(0编辑  收藏  举报

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