# Find Excel column number from column title

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

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

Examples:

```Input : A
Output : 1

Input : AA
Output : 27```

The process is similar to binary to decimal conversion. For example to convert AB, we do 26 * 1 + 2. As another example, to convert CDA, we do 3*26*26 + 4*26 + 1

`// C++ program to return title to resul`
`// of excel sheet.`
`#include <bits/stdc++.h>`
`using` `namespace` `std;`
`// Returns resul when we pass title.`
`int` `titleToNumber(string s)`
`{`
`    ``// This process is similar to binary-to-`
`    ``// decimal conversion`
`    ``int` `result = 0;`
`    ``for` `(``const` `auto``& c : s)`
`    ``{`
`        ``result *= 26;`
`        ``result += c  - ``'A'` `+ 1;`
`    ``}`
`    ``return` `result;`
`}`
`// Driver function`
`int` `main()`
`{`
`    ``cout << titleToNumber(``"CDA"``) << endl;`
`    ``return` `0;`
`}`

Output:

`2133`

Time Complexity = O(n) where n is length of input string.

Disclaimer: This does not belong to TechCodeBit, its an article taken from the below
source and credits.
source and credits:http://www.geeksforgeeks.org/find-excel-column-number-column-title/
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rakesh

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