excel-sheet-column-title

Excel Sheet Column Title – LeetCode 168

Problem

Description

Given a positive integer, return its corresponding column title as appear in an Excel sheet.

Example

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

Answer

Original

Code

class Solution {
public:
    string convertToTitle(int n) {
        string result;
        string alpha = "ZABCDEFGHIJKLMNOPQRSTUVWXY";
        while(n > 26){
            result = alpha[n % 26] + result;
            n -= n % 26? n % 26: 26;
            n /= 26;
        }
        result = alpha[n % 26] + result;
        return result;
    }
};

思路

简单的26进制转化，麻烦在于不已0为起始，所以要注意alpha的构造。时间复杂度$O(n)$，空间复杂度$O(1)$。
耗时$0$ ms，排名$84.25\%$

Better

思路

近似的思路，简洁的写法。时间复杂度$O(n)$，空间复杂度$O(1)$。
耗时$0$ ms，排名$84.25\%$

Code

class Solution {
public:
    string convertToTitle(int n) {
        string ans;
        while (n) {
            ans = char ((n - 1) % 26 + 'A') + ans;
            n = (n - 1) / 26;
        }
        return ans;
    }
};