【leetcode】171. Excel Sheet Column Number

一、题目描述

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

For example:

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

c++代码（8ms）

思路：先找规律，找到规律后很容易就能写出代码

#include<iostream>
#include<string>
#include<math>
using namespace std;

class Solution {
public:
int titleToNumber(string s) {
int len=s.length();
int result = 0;
for(int i = 1; i<=len; i++)
result += pow(26, i-1) * (s[len-i] - 'A' + 1);
return result;
}
};

看了一下discuss，大神的代码如下：

java

int result = 0;
for (int i = 0; i < s.length(); result = result * 26 + (s.charAt(i) - 'A' + 1), i++);
return result;
c++
int result = 0;
for (int i = 0; i < s.size(); result = result * 26 + (s.at(i) - 'A' + 1), i++);
return result;

python
return reduce(lambda x, y : x * 26 + y, [ord(c) - 64 for c in list(s)])