leetcode--171 Excel Sheet Column Number

Excel Sheet Column Number

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Question Solution 

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.

/// 相当于是26进制 

例如 AA=1*26+1;  AB=1*26+2   ;  BA=2*26+1=53;

class Solution {public:    int titleToNumber(string s) {        int n=s.length(),i,s1='A';        for(i=0;i<n;i++)        {            s1=(s1-'A')*26+s[i]-'A'+1;            s1=s1+'A';        }        return s1-'A';    }};