[#3516] feat(note): add description

problems/3516-find-closest-person/README.md

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+# [3516] Find Closest Person
+
+## 題目資訊
+- **難度**: Easy
+- **標籤**: Math
+- **題目連結**: [LeetCode](https://leetcode.com/problems/find-closest-person/)
+- **練習日期**: 2025-09-04
+
+## 題目描述
+You are given three integers `x`, `y`, and `z`, representing the positions of three people on a number line:
+
+`x` is the position of Person 1.
+`y` is the position of Person 2.
+`z` is the position of Person 3, who does **not** move.
+Both Person 1 and Person 2 move toward Person 3 at the same speed.
+
+Determine which person reaches Person 3 first:
+
+Return 1 if Person 1 arrives first.
+Return 2 if Person 2 arrives first.
+Return 0 if both arrive at the same time.
+Return the result accordingly.
+
+## 解題思路
+
+### 初步分析
+- 這題主要考察什麼概念？
+   距離計算和比較。使用絕對值計算兩點間距離
+- 有什麼關鍵限制條件？
+   比較兩個距離的大小關係
+- 預期時間/空間複雜度？
+   時間 O(1)，空間 O(1) - 只需要常數時間的計算
+
+### 解法概述
+**解法**: 
+   - 思路：
+      分別計算 Person 1 和 Person 2 到 Person 3 的距離，直接比較大小
+   - 時間複雜度：O(1)
+   - 空間複雜度：O(1)
+
+## 測試案例
+
+### 範例輸入輸出
+```
+Input: x = 2, y = 7, z = 4
+Output: 1
+Explanation: 
+- Person 1 is at position 2 and can reach Person 3 (at position 4) in 2 steps.
+- Person 2 is at position 7 and can reach Person 3 in 3 steps.
+Since Person 1 reaches Person 3 first, the output is 1.
+```
+
+### 邊界情況
+`1 <= x, y, z <= 100`
+
+## 學習筆記
+
+### 今天學到什麼？
+- 稍微練習了一下go func
+
+### 遇到的困難
+- 無
+
+### 改善方向
+- 無
+
+### 相關題目
+
+---
+**總結**: 今天這題考弱智?