Problem:

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 
    ...

Example 1:

Input: 1
Output: "A"

Example 2:

Input: 28
Output: "AB"

Example 3:

Input: 701
Output: "ZY"

思路：

Solution (C++):

string convertToTitle(int n) {
    vector<int> bit;
    string ans = "";
    while (n) {
        bit.push_back(n%26);
        n /= 26;
    }
    int len = bit.size();
    for (int i = 0; i < len-1; ++i) {
        if (bit[i] == 0) {
            bit[i] += 26;
            --bit[i+1];
        }
    }
    for (int i = len-1; i >= 0; --i) {
        if (bit[i] != 0)
            ans += ('A' + bit[i] - 1);
    }
    return ans;
}

性能：

Runtime: 0 ms  Memory Usage: 6.3 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB