Related to question Excel Sheet Column Title
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
Credits:
Special thanks to @ts for adding this problem and creating all test cases.
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class Solution { public: int titleToNumber(string s) { int n = s.size(), res = 0; for (int i = 0; i < n; ++i) res += (toupper(s[i]) - ‘A‘ + 1) * (int)pow(26, n - i - 1); return res; } };
不使用pow函数的改进：
class Solution { public: int titleToNumber(string s) { int n = s.size(), res = 0, i = 0; for (; i < n - 1; ++i) { //注意不能循环到n-1，防止溢出 res += (toupper(s[i]) - ‘A‘ + 1); res *= 26; } return res + (toupper(s[i]) - ‘A‘ + 1); } };
[LeetCode]61. Excel Sheet Column Number Excel列序号
原文：http://www.cnblogs.com/aprilcheny/p/4943338.html