String after processing backspace characters

Given a string S containing letters and '#'. The '#" represents a backspace. The task is to print the new string without '#'.

Examples: 

Input : S = "abc#de#f#ghi#jklmn#op#"
Output : abdghjklmo

Input : S = "##geeks##for##geeks#"
Output : geefgeek

Approach: A simple approach to this problem by using deque is as follows:

• Traverse the string S.
• If any character except '#' is found push it at back in deque.
• if the character '#' is found pop a character from back of deque.
• Finally pop all elements from front of deque to make new string.

Below is the implementation of above approach: 

geefgeek

Complexity Analysis:

• Time Complexity: O(N), where N is the length of the String.
• Space Complexity: O(N) since using auxiliary deque