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  • 1.(字符串)-获取字符串的最长回文子串

    如:'abcdzdcab',返回:cdzdc

    'abcdzdcab111',返回:cdzdc

    python:

    # 1穷举
    class Solution:
        def str(self, s):
            if not s:
                return ''
            n = len(s)
            logest, left, right = 0, 0, 0    #最大回文长度,最大回文左右位置
            for i in range(0, n):
                for j in range(i + 1, n + 1):
                    substr = s[i:j]    #截取i:j的子串,判断子串是不是回文,且标记最大回文
                    if self.isPalindrome(substr) and len(substr) > logest:
                        logest = len(substr)
                        left, right = i, j
            return s[left:right]
    
        def isPalindrome(self, s):
            if not s:
                return False
            #仅考虑纯字母,[::-1]反转字符
            return s == s[::-1]
    
    #2,分奇偶情况,对称判定。
    class Solution2:
        def str(self, s):
            if s == None or len(s) == 0:
                return s
            res = ''
            for i in range(len(s)):
                # 奇数情况,左右都是i开始,为对称轴两边取字母延伸
                t = self.pali(s, i, i)
                #保留最大回文串
                if len(t) > len(res):
                    res = t
                #     偶数情况
                t = self.pali(s, i, i + 1)
                if len(t) > len(res):
                    res = t
            return res
    
        def pali(self, s, l, r):
            #只要左边l,右边r不到顶端,且左右位置字母相等,就一直遍历
            while l >= 0 and r < len(s) and s[l] == s[r]:
                l -= 1
                r += 1
            #返回l,r两边扩展寻找回文字符串
            return s[l + 1:r]
    
    
    s = Solution()
    # s2 = Solution2()
    print(s.str('abcdzdcab'))
    # print(s2.str('abcdzdcab111'))
    
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  • 原文地址:https://www.cnblogs.com/onenoteone/p/12441786.html
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