The Word Break Problem
Objective : Given an string and a dictionary of words, find out if the input string can be broken into a space-separated sequence of one or more dictionary words.
dictionary = ["I" , "have", "Jain", "Sumit", "am", "this", "dog"] String = "IamSumit" Output: "I am Sumit" String ="thisisadog" Output : String can't be broken
Approach: Backtracking- Naive Approach
- Navigate the given input string.
- Take a blank string and keep adding one character at a time to it.
- Keep checking if the word exist in the dictionary.
- If word exist in the dictionary then add that word to the answer string and make recursive call to the rest of the string.
- If any of the recursive call returns false then backtrack and remove the word from the answer string and again keep adding the characters to string.
- If all the recursive calls return true that means string has been broken successfully.
- See the code for better explanation.
If we notice here we aresolving many sub-problems repeatedly.
Dynamic Programming to Rescue:
- We will use top-down approach.
- Before we solve it for any string check if we have already solve it.
- We can use another HashMap to store the result of already solved strings.
- Whenever any recursive call returns false, store that string in HashMap.
- See the code for better explanation
Output: this is sumit jain