Decode a string recursively encoded as count followed by substring
An encoded string (s) is given, the task is to decode it. The pattern in which the strings are encoded is as follows.
<count>[sub_str] ==> The substring 'sub_str' appears count times.
Input : str = "1[b]" Output : b Input : str = "2[ab]" Output : abab Input : str = "2[a2[b]]" Output : abbabb Input : str = "3[b2[ca]]" Output : bcacabcacabcaca
The idea is to use two stacks, one for integers and another for characters.
Now, traverse the string,
- Whenever we encounter any number, push it into the integer stack and in case of any alphabet (a to z) or open bracket (‘[‘), push it onto the character stack.
- Whenever any close bracket (‘]’) is encounter pop the character from the character stack until open bracket (‘[‘) is not found in the character stack. Also, pop the top element from the integer stack, say n. Now make a string repeating the popped character n number of time. Now, push all character of the string in the stack.
Below is the implementation of this approach:
<!—-Illustration of above code for “3[b2[ca]]”>
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