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Word Break II in Python
Suppose we have a non-empty string s and a dictionary called wordDict, this dictionary is containing a list of non-empty words, add spaces in s to construct a sentence where each word is a valid dictionary word. We have to find all such possible sentences. “appleraincoat” and dictionary is [“app”, “apple”, “rain”, “coat”, “raincoat”]
To solve this, we will follow these steps −
Create one map memo
Define a method called solve, this will take string and wordDict
if s is null, then return empty list
if s in memo, then −
return memo[s]
create an array ret
for i in range 1 to size of s
if substring of s from index 0 to i – 1 present in wordDict, then
for j in solve(substring of s from i to end, wordDict)
p := substring of s from index 0 to i – 1, concatenate with space and j, then clear extra space from left and right −
insert p into ret
memo[s] := ret
return memo[s]
Example
Let us see the following implementation to get better understanding −
class Solution(object):
def wordBreak(self, s, wordDict):
self.memo = {}
wordDict = set(wordDict)
return self.solve(s,wordDict)
def solve(self,s, wordDict):
if not s:
return ['']
if s in self.memo:
return self.memo[s]
ret = []
for i in range(1,len(s)+1):
if s[:i] in wordDict:
for j in self.solve(s[i:],wordDict):
ret.append((s[:i] + " " + j).strip())
self.memo[s] = ret
return self.memo[s]
ob = Solution()
print(ob.wordBreak("appleraincoat",["app","apple","rain","coat","rain coat"]))Input
"appleraincoat" ["app","apple","rain","coat","raincoat"]
Output
['apple rain coat', 'apple raincoat']
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