Update readme.md

Author: iamAntimPal

LeetCode SQL 50 Solution/1204. Last Person to Fit in the Bus/readme.md

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+Here's a well-structured `README.md` file for **LeetCode 1204 - Last Person to Fit in the Bus**, formatted for a GitHub repository:
+
+```md
+# 🚌 Last Person to Fit in the Bus - LeetCode 1204
+
+## 📌 Problem Statement
+You are given the **Queue** table, which contains information about people waiting for a bus.
+
+### Queue Table
+| Column Name | Type    |
+| ----------- | ------- |
+| person_id   | int     |
+| person_name | varchar |
+| weight      | int     |
+| turn        | int     |
+
+- **person_id** contains unique values.
+- The **turn** column determines the order in which people will board (`turn = 1` means the first person to board).
+- The **bus has a weight limit of 1000 kg**.
+- Only **one person can board at a time**.
+
+### Task:
+Find **the last person** who can board the bus **without exceeding the 1000 kg weight limit**.
+
+---
+
+## 📊 Example 1:
+### Input:
+**Queue Table**
+| person_id | person_name | weight | turn |
+| --------- | ----------- | ------ | ---- |
+| 5         | Alice       | 250    | 1    |
+| 4         | Bob         | 175    | 5    |
+| 3         | Alex        | 350    | 2    |
+| 6         | John Cena   | 400    | 3    |
+| 1         | Winston     | 500    | 6    |
+| 2         | Marie       | 200    | 4    |
+
+### Output:
+| person_name |
+| ----------- |
+| John Cena   |
+
+### Explanation:
+Ordering by `turn`:
+| Turn | ID  | Name      | Weight | Total Weight |
+| ---- | --- | --------- | ------ | ------------ |
+| 1    | 5   | Alice     | 250    | 250          |
+| 2    | 3   | Alex      | 350    | 600          |
+| 3    | 6   | John Cena | 400    | 1000         | ✅ (last person to board) |
+| 4    | 2   | Marie     | 200    | 1200         | ❌ (exceeds limit)        |
+| 5    | 4   | Bob       | 175    | ❌            |
+| 6    | 1   | Winston   | 500    | ❌            |
+
+---
+
+## 🖥 SQL Solution
+
+### 1️⃣ Standard MySQL Solution
+#### Explanation:
+- **Use a self-join** to accumulate the total weight up to each person's turn.
+- **Filter out** people whose cumulative weight exceeds **1000**.
+- **Find the last person** who can board.
+
+```sql
+SELECT a.person_name
+FROM
+    Queue AS a,
+    Queue AS b
+WHERE a.turn >= b.turn
+GROUP BY a.person_id
+HAVING SUM(b.weight) <= 1000
+ORDER BY a.turn DESC
+LIMIT 1;
+```
+
+---
+
+### 📝 Step-by-Step Breakdown:
+
+1️⃣ **Self-Join on the Table**
+```sql
+FROM Queue AS a, Queue AS b
+WHERE a.turn >= b.turn
+```
+- This pairs each row `a` with all rows `b` where `b.turn` is less than or equal to `a.turn`.
+- Allows us to calculate the **cumulative sum of weights** for each person.
+
+2️⃣ **Group by Each Person**
+```sql
+GROUP BY a.person_id
+```
+- Groups all rows by `person_id` so we can perform calculations per person.
+
+3️⃣ **Compute the Cumulative Weight**
+```sql
+HAVING SUM(b.weight) <= 1000
+```
+- Filters out people whose cumulative boarding weight exceeds **1000 kg**.
+
+4️⃣ **Find the Last Person Who Can Board**
+```sql
+ORDER BY a.turn DESC
+LIMIT 1;
+```
+- **Sorts by turn in descending order** so that we find the **last person** who can board.
+- **Limits to 1 row** to return only the last eligible person.
+
+---
+
+## 🐍 Pandas Solution (Python)
+#### Explanation:
+- **Sort by `turn`** to simulate the boarding order.
+- **Compute the cumulative sum** of weights.
+- **Find the last person** whose weight sum **does not exceed 1000**.
+
+```python
+import pandas as pd
+
+def last_person_to_fit(queue: pd.DataFrame) -> pd.DataFrame:
+    # Sort by turn
+    queue = queue.sort_values(by="turn")
+
+    # Compute cumulative weight sum
+    queue["cumulative_weight"] = queue["weight"].cumsum()
+
+    # Filter those who fit on the bus
+    queue = queue[queue["cumulative_weight"] <= 1000]
+
+    # Return the last person to fit
+    return queue.tail(1)[["person_name"]]
+```
+
+---
+
+## 📁 File Structure
+```
+📂 Last-Person-Fit
+│── 📜 README.md
+│── 📜 solution.sql
+│── 📜 solution_pandas.py
+│── 📜 test_cases.sql
+```
+
+---
+
+## 🔗 Useful Links
+- 📖 [LeetCode Problem](https://leetcode.com/problems/last-person-to-fit-in-the-bus/)
+- 📚 [SQL `GROUP BY` Clause](https://www.w3schools.com/sql/sql_groupby.asp)
+- 🐍 [Pandas cumsum() Documentation](https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.cumsum.html)
+```
+
+This README includes:
+- **Problem statement**
+- **Example input and output**
+- **SQL solution with explanations**
+- **Pandas solution in Python**
+- **File structure for GitHub**
+- **Useful links**
+
+Let me know if you need any modifications! 🚀