# [3025] Find The Number Of Ways To Place People I

## 題目資訊
- **難度**: Medium
- **標籤**: Array, Math, Geometry, Sorting, Enumeration
- **題目連結**: [LeetCode](https://leetcode.com/problems/find-the-number-of-ways-to-place-people-i/)
- **練習日期**: 2025-09-02

## 題目描述
You are given a 2D array `points` of size `n x 2` representing integer coordinates of some points on a 2D plane, where `points[i] = [xi, yi]`.

Count the number of pairs of points `(A, B)`, where
 - `A` is on **the upper** left side of `B`, and
 - there are no other points in the rectangle (or line) they make (**including the border**).

Return the count.

## 解題思路

### 初步分析
- 這題主要考察什麼概念？
- 有什麼關鍵限制條件？
- 預期時間/空間複雜度？

### 解法概述
1. **暴力解法**: 
   - 思路：
   - 時間複雜度：O(?)
   - 空間複雜度：O(?)
   
2. **優化解法**: 
   - 思路：
   - 時間複雜度：O(?)
   - 空間複雜度：O(?)

## 測試案例

### 範例輸入輸出
```
Input: points = [[6,2],[4,4],[2,6]]
Output: 2
Explanation:
 - The left one is the pair (points[1], points[0]), where points[1] is on the upper left side of points[0] and the rectangle is empty.
 - The left one is the pair (points[1], points[0]), where points[1] is on the upper left side of points[0] and the rectangle is empty.
 - The right one is the pair (points[2], points[0]), where points[2] is on the upper left side of points[0], but points[1] is inside the rectangle so it's not a valid pair.
```

### 邊界情況
- `2 <= n <= 50`
- `points[i].length == 2`
- `0 <= points[i][0], points[i][1] <= 50`
- All `points[i]` are distinct.

## 學習筆記

### 今天學到什麼？
- 

### 遇到的困難
- 

### 改善方向
- 

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**總結**: 這題的核心概念是...，適合練習...技巧。