[LeetCode]168.Excel Sheet Column Title

【题目】

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

For example:

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

【分析】

Becauseany_pos_int mod 26should return a number in the interval[0, 25], but what we want is a number in the interval[1, 26]. Thus we have to shift the digit leftward by1which means--n.

【代码】

/*********************************
*   日期：2015-01-29
*   作者：SJF0115
*   题目: 168.Excel Sheet Column Title
*   网址：https://oj.leetcode.com/problems/excel-sheet-column-title/
*   结果：AC
*   来源：LeetCode
*   博客：
**********************************/
#include <iostream>
#include <vector>
#include <string>
using namespace std;

class Solution {
public:
    string convertToTitle(int n) {
        if(n <= 0){
            return "";
        }//if
        vector<int> vec;
        --n;
        // 除26取余倒排序
        while(n >= 0){
            vec.push_back(n % 26);
            n /= 26;
            --n;
        }//
        // 转换
        string result;
        int len = vec.size();
        for(int i = 0;i < len;++i){
            result.insert(result.begin(),vec[i]+'A');
        }//for
        return result;
    }
};

int main(){
    Solution solution;
    for(int i = 500;i < 800;++i){
        string result = solution.convertToTitle(i);
        // 输出
        cout<<result<<" ";
    }
    cout<<endl;
    return 0;
}

【代码二】

class Solution {
public:
    string convertToTitle(int n) {
        if(n <= 0){
            return "";
        }//if
        string result;
        // 除26取余倒排序
        while(n > 0){
            n --;
            result.insert(result.begin(),static_cast<char>(n % 26 + 'A'));
            n /= 26;
        }//
        return result;
    }
};