display the first three rows core interview pattern 模式
1 道题目
模式页适合用来建立可复用解题框架。先识别题目特征，再按固定流程解释状态定义、转移和边界。
识别信号
- Check if the candidate is familiar with pandas functions like head().
- Observe if the candidate optimizes for readability and performance when handling DataFrames.
解题流程
- 1. 明确窗口/状态定义
- 2. 更新状态并维护约束
- 3. 用边界样例验证
常见失分点
- Not using the head() function or slicing, leading to unnecessary iterations over the entire DataFrame.