How to solve the problem of column names in a given Excel table and returning their corresponding column serial numbers

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Topic description

Given a column name in an Excel table, return its corresponding column number.

For example,

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

Example 1:

Input: "A" output: 1

Example 2:

Input: "AB" output: 28

Example 3:

Input: "ZY" output: 701 solution

Tags: string traversal, binary conversion

The initialization result ans = 0, and each letter is subtracted with A during ergodicity. Because A represents 1, each number needs to be added by 1 after subtraction, and the numerical value num = letter -'A' + 1 is calculated.

Because there are 26 letters, it is equivalent to 26 digits, with one digit for every 26 numbers.

So one bit per pass is ans = ans * 26 + num.

Take ZY as an example, if the value of Z is 26 and the value of Y is 25, the result is 26 * 26 + 250701.

Time complexity: O (n)

The code class Solution {public int titleToNumber (String s) {int ans = 0; for (int iTunes)