168.Excel Sheet Column Title
Given an integer columnNumber, return its corresponding column title as it appears in an Excel sheet.
For example:
1
2
3
4
5
6
7
8
| A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28
...
|
Example 1:
1
2
| Input: columnNumber = 1
Output: "A"
|
Example 2:
1
2
| Input: columnNumber = 28
Output: "AB"
|
Example 3:
1
2
| Input: columnNumber = 701
Output: "ZY"
|
时间复杂度：O(log26columnNumber)
空间复杂度：O(1)
1
2
3
4
5
6
7
8
9
10
11
12
| class Solution {
public:
string convertToTitle(int columnNumber) {
string ans_s = "";
while (columnNumber != 0) {
ans_s += (columnNumber - 1) % 26 + 'A';
columnNumber = (columnNumber - (columnNumber - 1) % 26 - 1) / 26;
}
reverse(ans_s.begin(), ans_s.end());
return ans_s;
}
};
|
代码优化：
时间复杂度：O(log26columnNumber)
空间复杂度：O(1)
1
2
3
4
5
6
7
8
9
10
11
12
13
| class Solution {
public:
string convertToTitle(int columnNumber) {
string ans;
while (columnNumber > 0) {
--columnNumber;
ans += columnNumber % 26 + 'A';
columnNumber /= 26;
}
reverse(ans.begin(), ans.end());
return ans;
}
};
|