Here’s a clear explanation and a Python solution for the **Reverse Parenthesis** problem.

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## ✅ **Problem Summary**

Given a string with **properly nested parentheses**, decode it using these rules:

1. **Reverse** the characters inside each pair of parentheses.
2. **Remove all parentheses** in the final output.
3. Process from **innermost → outward**.

Example:
`"a(bc(def)g)h"` →
Innermost: `"def"` → `"fed"`
Next: `"bcfedg"` → `"gdefcb"`
Final: `"agdefcbh"`

---

## ✅ **Python Solution (Stack-Based)**

```python
def reverse_parentheses(s: str) -> str:
    stack = []
    
    for char in s:
        if char == ')':
            # Pop until '('
            buffer = []
            while stack and stack[-1] != '(':
                buffer.append(stack.pop())
            stack.pop()  # remove '('

            # Push reversed content back to stack
            for c in buffer:
                stack.append(c)
        else:
            stack.append(char)

    return ''.join(stack)
```

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## ✅ **How it Works**

* Use a **stack** to hold characters.
* When encountering `)`, pop characters until `(` to get the innermost substring.
* Since popping reverses the substring automatically, just push reversed characters back.
* Continue until complete, then join the stack into a result string.

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## ✅ **Example**

```python
print(reverse_parentheses("a(bc(def)g)h"))
```

Output:

```
agdefcbh
```

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If you'd like, I can:

* Provide a version without using a stack
* Add more examples
* Explain step-by-step with diagrams
* Write a solution in another language (JavaScript, Java, C++, etc.)