Leetcode: Word Break

Question

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words.

For example, given

s = “leetcode”,
dict = [“leet”, “code”].

Return true because “leetcode” can be segmented as “leet code”.

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Solution

Analysis

Get idea from Code Ganker”s 优快云

if using recursive function, the one substring will be calculated many times. That’s why we use dynamic programming. flag[i] records whether substring[0:i+i] is satisfied.

Code

class Solution(object):
    def wordBreak(self, s, wordDict):
        """
        :type s: str
        :type wordDict: Set[str]
        :rtype: bool
        """

        if s=='':
            return True 

        flag = [False]*(len(s)+1)
        flag[0] = True

        for ind in range(len(s)):
            newstr = s[:ind+1]
            for inind in range(len(newstr)):
                if flag[inind] and newstr[inind:] in wordDict:
                    flag[ind+1] = True
                    break

        return flag[len(s)]