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Decode String

Certification: Intermediate Level Accuracy: 0% Submissions: 0 Points: 10

Write a C program to decode a run-length encoded string. The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets should be repeated exactly k times. You may assume that the input string is always valid with properly nested brackets.

Example 1
    
  
  • Input: s = "3[a]2[bc]"
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  • Output: "aaabcbc"
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  • Explanation:

    •  Step 1: "3[a]" means repeat "a" 3 times, resulting in "aaa".

    •  Step 2: "2[bc]" means repeat "bc" 2 times, resulting in "bcbc".

    •  Step 3: Concatenate the results: "aaa" + "bcbc" = "aaabcbc".
    •
Example 2
    
  
  • Input: s = "2[abc]3[cd]ef"
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  • Output: "abcabccdcdcdef"
    • 
  
  • Explanation:

    •  Step 1: "2[abc]" means repeat "abc" 2 times, resulting in "abcabc".

    •  Step 2: "3[cd]" means repeat "cd" 3 times, resulting in "cdcdcd".

    •  Step 3: Concatenate with "ef": "abcabc" + "cdcdcd" + "ef" = "abcabccdcdcdef".
    •
Constraints
    
  
  • 1 ≤ s.length ≤ 30
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  • s consists of lowercase English letters, digits, and square brackets '[]'
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  • s is guaranteed to be a valid input
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  • Time Complexity: O(n)
    • 
  
  • Space Complexity: O(n)
    •
StringsStackCapgeminiSamsung
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Hint
Solution

Solution Hints

    
  
  • Use a stack-based approach to handle nested brackets.
    • 
  
  • Use two stacks: one for numbers and one for strings.
    • 
  
  • When you encounter '[', push current number and string to stacks.
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  • When you encounter ']', pop from stacks and repeat the string.
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  • Build the result string character by character.
    •

Steps to solve by this approach:

 Step 1: Initialize two stacks - one for numbers and one for strings, along with a result string.
 Step 2: Iterate through each character in the input string.
 Step 3: If character is a digit, parse the complete number and push to number stack.
 Step 4: If character is '[', push current result to string stack and reset result.
 Step 5: If character is ']', pop number and string from stacks, repeat current result and concatenate.
 Step 6: If character is a regular letter, append it to the current result string.
 Step 7: Return the final result string after processing all characters.

Submitted Code :