這次跟大家分享一下我在 Capital One OA 裡遇到的兩道題，整體風格還是比較典型的北美銀行類大廠筆試：既考演算法思路的紮實度，又考對邏輯條件的精準把握。 第一題是摩天大樓數位裡的最大正方形面積，思路上很像「二分答案 + 區間驗證」; 第二題則是矩陣里統計“近規則十字”，重點在於對頻次分佈和中心元素特殊性的理解。 兩道題看似獨立，其實都要求寫出 clean code + 高效解法，否則很容易在時間里卡住。
Question 1: Largest Square Area
Problem:
You are given an array of integers representing the heights of skyscrapers in a row.
Find the maximum area of a square that can be placed among these buildings.
- A square of side length
mcan be placed if there exists a contiguous subarray of lengthmwhere every building’s height is at leastm. - The output should be the largest possible square area (
m²).
Example 1:
Input: heights = [3, 1, 3, 4, 3, 5]
Output: 9
Explanation:
The maximum square has side length 3 (for example, subarray [3,4,3] or [4,3,5]).
Area = 3 * 3 = 9.
Example 2:
Input: heights = [2, 2, 2]
Output: 4
Explanation:
The maximum square has side length 2 (subarray [2,2]).
Area = 2 * 2 = 4.
Question 2: Count of Nearly-Regular Crosses
Problem:
You are given a 2D integer matrix. A “nearly-regular cross” is defined as follows:
- A cross is formed by choosing a cell as the center, taking its row as the horizontal arm and its column as the vertical arm.
- Collect all numbers appearing in that row and column.
- If all numbers are identical, it is a regular cross (valid).
- If there are exactly two distinct numbers and one of them appears only once, and that unique element is the center cell, then it is a nearly-regular cross (also valid).
- Otherwise, it is not valid.
Return the total number of valid (regular + nearly-regular) crosses in the matrix.
Example 1:
Input:
matrix = [
[1, 1, 1],
[1, 2, 1],
[1, 1, 1]
]
Output: 1
Explanation:
Only the center cell (value 2 at position [1,1]) forms a nearly-regular cross.
All rows/columns contain only 1s except the center element = 2, so it is valid.
Example 2:
Input:
matrix = [
[5, 5, 5],
[5, 5, 5],
[5, 5, 5]
]
Output: 9
Explanation:
Every cell can be chosen as the center, and all of them form a regular cross.
Total = 9.
如果你也在準備 Capital One、Citadel、或者 Amazon 這一類 OA/VO，其實完全不用單打獨鬥。Programhelp 可以給你提供無痕遠端連線助攻：比如即時語音提醒、debug 思路點撥、代碼結構優化，讓你在緊張的考試環境里少走彎路，把精力放在思考而不是卡殼上。 很多同學反饋說，有了及時的提醒，就能穩定輸出高品質答案，大大提升通過率。
