168. Excel Sheet Column Title

📋 Đề Bài

Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.

For example:

A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28 
...

Example 1:

Input: columnNumber = 1
Output: "A"

Example 2:

Input: columnNumber = 28
Output: "AB"

Example 3:

Input: columnNumber = 701
Output: "ZY"

Constraints:

1 <= columnNumber <= 2³¹ - 1

🧠 Thuật Toán & Kỹ Thuật

String (Chuỗi)

⏱️ Thời gian O(n)

💾 Không gian O(1)

💻 Lời Giải

C++ 0168-excel-sheet-column-title.cpp

class Solution {
public:
    string convertToTitle(int columnNumber) {
        int n = columnNumber;
        string s;
        while (n > 0) {
            n--;
            int m = n % 26;
            n /= 26;
            s.push_back(m + 'A');
        }
        reverse(s.begin(), s.end());
        return s;
    }
};