Given a stream of characters and we have to find first non repeating character each time a character is inserted to the stream.
Input : a a b c Output : a -1 b b Input : a a c Output : a -1 c
We have already discussed a Doubly linked list based approach in the previous post.
- Create a count array of size 26(assuming only lower case characters are present) and initialize it with zero.
- Create a queue of char datatype.
- Store each character in queue and increase its frequency in the hash array.
- For every character of stream, we check front of the queue.
- If the frequency of character at the front of queue is one, then that will be the first non repeating character.
- Else if frequency is more than 1, then we pop that element.
- If queue became empty that means there are no non repeating character so we will print -1.
Below is the implementation of above approach:
a -1 b b
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