[leetcode]Palindrome Partitioning II @ Python

原题地址:https://oj.leetcode.com/problems/palindrome-partitioning-ii/

题意:

Given a string s, partition s such that every substring of the partition is a palindrome.

Return the minimum cuts needed for a palindrome partitioning of s.

For example, given s = "aab",
Return 1 since the palindrome partitioning ["aa","b"] could be produced using 1 cut.

解题思路:由于这次不需要穷举出所有符合条件的回文分割,而是需要找到一个字符串s回文分割的最少分割次数,分割出来的字符串都是回文字符串。求次数的问题,不需要dfs,用了也会超时,之前的文章说过,求次数要考虑动态规划(dp)。对于程序的说明:p[i][j]表示从字符i到j是否为一个回文字符串。dp[i]表示从第i个字符到最后一个字符,最少的分割次数下,有多少个回文字符串,即分割次数+1。这道题动态规划的思路比较简单,直接上代码吧。

代码:

class Solution:
# @param s, a string
# @return an integer
# @dfs time out
# @dp is how many palindromes in the word
def minCut(self, s):
dp = [0 for i in range(len(s)+1)]
p = [[False for i in range(len(s))] for j in range(len(s))]
for i in range(len(s)+1):
dp[i] = len(s) - i
for i in range(len(s)-1, -1, -1):
for j in range(i, len(s)):
if s[i] == s[j] and (((j - i) < 2) or p[i+1][j-1]):
p[i][j] = True
dp[i] = min(1+dp[j+1], dp[i])
return dp[0]-1
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