131. Palindrome Partitioning

131. Palindrome Partitioning

找出所有可能要用回溯

class Solution(object):
    def partition(self, s):
        """
        :type s: str
        :rtype: List[List[str]]
        """
        res = []
        trace = []
        self.DFS(s, res, trace, 0)
        return res
    def DFS(self, s, res, trace, k):
        if k == len(s):
            res.append(trace[:])
        for i in range(k+1, len(s)+1):
            if self.isValid(s[k:i]):
                trace.append(s[k:i])
                self.DFS(s, res, trace, i)
                trace.pop()
    def isValid(self, s):
        return s and s == s[::-1]

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132. Palindrome Partitioning II

132. Palindrome Partitioning II

求一个结果要用动态规划

class Solution(object):
    def minCut(self, s):
        """
        :type s: str
        :rtype: int
        """
        dp = [i for i in range(len(s))]
        #dp[i]表示s[:i+1]需要几cut
        for i in range(len(s)):
            if self.isValid(s[:i+1]):
                dp[i] = 0
            else:
                for j in range(1, i+1):
                    if self.isValid(s[j:i+1]):
                        dp[i] = min(dp[i], dp[j-1] + 1)
                    else:
                        dp[i] = min(dp[i], dp[j-1] + i - j + 1)
        return dp[-1]
    def isValid(self, s):
        return s and s == s[::-1]