word break.py

'''
Given a string s and a dictionary of strings wordDict, return true if s can be segmented into a space-separated sequence of one or more dictionary words.

Note that the same word in the dictionary may be reused multiple times in the segmentation.

Example 1:

Input: s = "leetcode", wordDict = ["leet","code"]
Output: true
Explanation: Return true because "leetcode" can be segmented as "leet code".
Example 2:

Input: s = "applepenapple", wordDict = ["apple","pen"]
Output: true
Explanation: Return true because "applepenapple" can be segmented as "apple pen apple".
Note that you are allowed to reuse a dictionary word.
Example 3:

Input: s = "catsandog", wordDict = ["cats","dog","sand","and","cat"]
Output: false
'''
class Solution:
    def wordBreak( self, s , wordDict ):
        dp = [False] * (len(s) + 1)
        dp[len(s)] = True

        for i in range(len(s) - 1, -1 , -1):
            for word in wordDict:
                if (i + len(word)) <= len(s) and s[i:i+len(word)] == word:
                    dp[i] = dp[i+len(word)]
                if dp[i]:
                    break
        
        return dp[0]